MPLS

MPLS Label Distribution Parameters

MPLS Label Distribution Parameter Options:

Label Space Options	Per-Interface	Per-Plaform
Label Distribution	Unsolicited downstream	Downstream-on-Demand
Label Allocation	Independent Control Mode	Ordered Control Mode
Label Retention	Liberal Label Retention	Conservative Label Retention

---

Label Space Options

Per-Platform Labels

• LFIB: [Label | Action | Next Hop ]
• one label assigned to a destination network and announced to all neighbors
• locally unique, valid on all incoming interfaces
• smaller LFIB, FIB; faster label exchange
• less secure than per-interface labels; label-spoofing
• default in Frame-Mode MPLS

Per-Interface Labels

• LFIB:[IN intf | IN Label | NH intf | NH Label]
• one label for each destination, each device, each interface
• secure; prevents label-spoofing; labeled packets/ATM cells only accepted from interface where label is assigned
• default in Cell-Mode MPLS

---

Label Distribution

Unsolicited Downstream

• label advertised to all neighbor LSRs, regardless of whether upstream or downstream
• Frame-Mode

Downstream-On-Demand

• label advertised only upon request of upstream LSR
• cell-mode

---

Label Allocation 

Independent Control

• LSR can assign a label for a prefix w/o outgoing/downstream label
• for edge LSRs only (requires L3 capabilities)
• faster label propagation
• for unsolicited downstream / frame-mode

Ordered Control

• local label allocated and propagated only
• if exist(nexthop label) propagae/allocate label, else request label from nexthop
• for downstream-on-demand/cell-mode

---

Label Retention

Liberal Label Retention

• all received label stored in LIB, even if not from next-hop LSR
• improves convergence speed; allows easy failover for link failures
• frame-mode

Conservative Label Retention

• only received labels from nexthop LSRs are  stored; others are ignored
• downstream-on-demand/cell-mode

---

Standard Parameter Sets for Cisco Platforms

Parameter	Routers, frame interfaces	Routers, ATM interfaces	ATM switches
Label Space	per-platform	per-interface	per-interface
Label Distribution	unsolicited downstream	downstream-on-demand	downstream-on-demand
Label Allocation	independent control	independent control	ordered control
Label Retention	liberal label retention	conservative OR liberal	conservative

BGP

BGP Route Dampening

At a Glance: designed to reduce router processing load caused by unstable routes; prevents sustained routing oscillations without affecting well-behaved routes; RFC 2439: BGP Route Flap Dampening; minimizes BGP updates by suppressing unstable routes.

Route-Dampening Operation:

• EBGP route flaps = 1000 penalty points
• IBGP route flaps not dampened;
• penalty not user-configurable;
• penalty decays via exponential decay algorithm
• if penalty > suppress limit, route is dampened
• if penalty < reuse limit, dampened route is propagated
• if penalty < 1/2 reuse limit, flap history forgotten
• route is never dampened more than the maximum suppress time limit
• unreachable route with flap history is in history state (still in BGP table to retain flap history)
• penalty is applied to an individual path, not the prefix

---

Configuring Route Dampening:

router(config-router)# bgp dampening [half-life reuse suppress max-suppress-time] [route-map route-map-name]
half-life	time for penalty to halve (default 15 minutes)
reuse	penalty points when dampened route is reused (default 750)
suppress	penalty points when route is suppressed (default 2000)
max-suppress-time	maximum time a route is suppressed (default 1hour; maximum 255 minutes)

router(config-route-map)# set dampening half-life reuse suppress max-suppress-time

- used for less aggressive dampening of routes towards root DNS servers - dampening of smaller prefixes more aggressively - selective dampening based on BGP neighbors and route-map match criteria

Other Commands:

clear ip bgp ip_addr flap-statistics [{regexp regexp} | {filter-list listname} | {ipaddr mask} ]

clear ip bgp dampening [ipaddr mask]

show ip bgp dampened-paths

show ip bgp flap-statistics [{regexp regexp}|{filter-list listname}|{ipaddr mask [longer-prefix]}]

debug ip bgp dampening

Monday, May 23, 2011

BGP: Regular Expressions for AS-PATH Filtering

Symbol	Description
|	logical OR
.	match any
[x..y]	match one in range
^	match beginning of string
$	match end of string
_	match any delimiter/white space
( )	group as a single atom
*	match 0 or more instances of previous atom
?	match 0 or 1 instance of previous atom
+	match 1 or more instances of previous atom
\	escape character; if followed by a number n, points to the nth atom

Example 1: Advertise routes with empty AS-PATH (internal routes)

router bgp 123  neighbor 5.6.7.8 remote-as 387  neighbor 5.6.7.8 filter-list 1 out ! ip as-path access-list 1 permit ^$ !match "blank" atom at the "start" and "end" of string !

Example 2: Accept only default routes, preferring primary route based on AS PATH:

	AS387 (primary ISP)
	/
AS123
	\
	AS462 (backup ISP)

router bgp 123  neighbor 1.2.3.4 remote-as 462  neighbor 1.2.3.4 route-map FILTER in  neighbor 5.6.7.8 remote-as 387  neighbor 5.6.7.8 route-map FILTER in ! route-map FILTER permit 10 ! default routes from primary ISP (AS 387) accepted are preferred (larger weight)  match ip prefix-list DEFAULT_ONLY  match as-path 10  set weight 150 ! route-map FILTER permit 20 ! default routes from backup ISP are accepted, with lower preference than primary ISP routes  match ip prefix-list DEFAULT_ONLY  set weight 100 ! ip as-path access-list 10 permit _387$ ip prefix-list DEFAULT_ONLY seq 10 permit 0.0.0.0/0 !

Example 3: AS PATH Filtering with AS Path Prepending:

- customer in AS123 is performing AS-PATH pre-pending

AS123
10.0.0.1	\
	\
	AS462

router bgp 387  neighbor 10.0.0.1 remote-as 213  neighbor 10.0.0.1 filter-list 10 in ! ip as-path access-list 10 permit ^123(_123)*$ ! accepts "123", "123 123", or "123 123 123"

Example 4: AS PATH Filtering with AS Path Prepending, multiple customers:

- multiple customers performing AS PATH Prepending

Customer 1
	\
Customer 2 -	AS387
	/
Customer 3

!

router bgp 387  neighbor 10.0.0.1 remote-as 123  neighbor 10.0.0.1 filter-list 10 in  neighbor 20.0.0.1 remote-as 456  neighbor 20.0.0.1 filter-list 10 in  neighbor 30.0.0.1 remote-as 789  neighbor 30.0.0.1 filter-list 10 in ! ip as-path access-list 10 permit ^([0..9]+)(_\1)*$ ! accepts repeating instances of "123", "456", and "789" ! does not accept strings non-repeating strings (e.g. "123 123 100") !

Notes:
atom 1 = at least one instance of a number at the beginning of the string;
atom 2 = 0 or more instances of a whitespace and atom 1 until the end of the string.

Wednesday, May 4, 2011

BGP Path Attributes and Route Selection

BGP Path Attributes

Mandatory Well-Known  Origin (i, e, ?)  AS-Path (sequence of AS-Numbers to access network/IP)  Next-Hop (ip address)

Discretionary Well-Known  Local Preference (for routing policy)  Atomic Aggregate (flags route if aggregated)

Optional Non-Transitive  Multi-Exit Discriminator (MED) - multiple entry pts to one AS  Originator-ID - for route reflector environment  Cluster-List - for route reflector environment

Optional Transitive  Aggregator - IP address & AS of routers that aggregated routes  Community - for route tagging

BGP Route Selection Order:

1. Prefer highest weight (local to router)
2. Prefer highest local preference (global within AS)
3. Prefer routes that the router originated
4. Prefer shorter AS paths
5. Prefer lowest origin code (IGP < EGP < Incomplete)
6. Prefer lowest MED
7. Prefer external (EBGP) paths over internal (IBGP)
1. For IBGP paths, prefer nonreflected routes (no originator-ID) over reflected routes
2. For reflected routes, prefer shorter cluster-list
8. For IBGP paths, prefer path through closest IGP neighbor
9. For EBGP paths, prefer oldest (most stable) path
10. Prefer paths from router with the lower BGP router-ID

BGP: Multihomed Customer to Single ISP in Load-Sharing Setup with Static Routes

Outbound Traffic (CE to PE):
- each customer router uses closest CE as exit point;
- CE routers must be collocated to have load-sharing;

Inbound/Return Traffic (PE to CE) (pre-IOS 12.2):
- true load-sharing is impossible to achieve with multiple PEs;
- per BGP route selection, only one route will be the best route (to the customer network)
- can be optimized by dividing the customer address space

Customer Network: 11.2.3.0 /24
Customer Network "division" assigned to PE1: 11.2.3.0/25
Customer Network "division" assigned to PE2: 11.2.3.128/25

Read more »

BGP: Multihomed Customer to Single ISP in Primary-Backup Setup with Static Routes

Scenario:
Multihomed customer connected to a single service provider on multiple permanent links;
Customer network using OSPF; provider network using BGP; CE-PE via static routing;
Floating static routes configured as backup on both CE and PE;

Floating Static Routes in BGP:
Once active, the floating static routes will be permanently installed in BGP; static routes are locally sourced which is preferred;

• admin distance cannot be used in route-maps; hence, use communities
• tag floating static routes; tags mapped to specific communities;
• use route maps to modify the weight and/or local preference;
• default weight: 32768

Read more »

Wednesday, April 15, 2009

IOS: %BGP_MPLS-3-GEN_ERROR

Mar 18 20:41:38.892 EDT: %BGP_MPLS-3-GEN_ERROR: BGP: MPLS outlabel changed, MPLS forw not updated, prefix not in routing table -Traceback= 10D36950 10D3709C 10B10388 10B10718 10AEEFD0 10AEF030 10B53A50 10B53DC0 10AF588C 10AFD610 10AFE8E0 10A44524 10A3B6D4
Mar 18 20:41:38.892 EDT: %BGP_MPLS-3-GEN_ERROR: BGP: MPLS outlabel changed, MPLS forw not updated, prefix not in routing table -Traceback= 10D36950 10D3709C 10B10388 10B10718 10AEEFD0 10AEF030 10B53A50 10B53DC0 10AF588C 10AFD610 10AFE8E0 10A44524 10A3B6D4
Mar 18 20:41:38.892 EDT: %BGP_MPLS-3-GEN_ERROR: BGP: MPLS outlabel changed, MPLS forw not updated, prefix not in routing table -Traceback= 10D36950 10D3709C 10B10388 10B10718 10AEEFD0 10AEF030 10B53A50 10B53DC0 10AF588C 10AFD610 10AFE8E0 10A44524 10A3B6D4


Cisco IOS Software, Catalyst 4500 L3 Switch Software (cat4500e-ENTSERVICES-M), Version
12.2(50)SG1, RELEASE SOFTWARE (fc2)
Technical Support:
http://www.cisco.com/techsupport
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Tue 10-Feb-09 00:17 by prod_rel_team
Image text-base: 0x10000000, data-base: 0x124FED8C

ROM: 12.2(44r)SG
Darkside Revision 0, Jawa Revision 11, Tatooine Revision 140, Forerunner Revision 1.74

MyRouter uptime is 5 days, 3 hours, 12 minutes
System returned to ROM by power-on
System restarted at 19:50:40 EDT Fri Mar 13 2009
System image file is "bootflash:/cat4500e-entservices-mz.122-50.SG1.bin"

cisco WS-C4900M (MPC8548) processor (revision 2) with 524288K bytes of memory.
Processor board ID JAE130628BD
MPC8548 CPU at 1.33GHz, Cisco Catalyst 4900M
Last reset from PowerUp
1 Virtual Ethernet interface
36 Gigabit Ethernet interfaces
16 Ten Gigabit Ethernet interfaces
511K bytes of non-volatile configuration memory.

Configuration register is 0x2102

---

CSCse15707: Trace back seen at bgp_ipv4_mpls_label_change.

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCse15707

CCNP Basics | IT HELP (CCNA,CCNP,MCSE,LINUX,VMWARE,CLOUD MGN)

CCNP Basics | IT HELP (CCNA,CCNP,MCSE,LINUX,VMWARE,CLOUD MGN)

CCNP Basics

1. Types of Routes - Static Routes and Dynamic Routes

Routing is the process of selecting paths in a network along which to send network traffic and route is the path to send the network traffic.
There are two ways a router learn a route: static and dynamic. A static route is a route that is manually configured on the router. Simply we can say a static route is a route that is created manually by a network administrator. The information about the networks that are directly connected to the active router interfaces are added to the routing table initially and they are known as connected routes. The second way that the router can learn static routes are by configuring the routes manually.
Dynamic routes are routes that a router learns by using a routing protocol. Routing protocols will learn about routes from other neighbouring routers running the same routing protocol. Dynamic routing protocols share network numbers a router knows about and how to reach these networks. Through this sharing process, a router can learn about all of the reachable network numbers in the network.

2. What is the difference between Routing Protocols and Routed Protocols

While discussing about protocols, two terms are commonly used: routing protocols and routed protocols. A routing protocol learns routes for a routed protocol and routed protocol carries user traffic such as e-mail, file transfers etc. IP, IPX and Appletalk are the examples of Routed Protocols. An example of Routing Protocol is OSPF (Open Shortest Path First).

Routed Protocol	Routing Protocols
IP	RIP, IGRP, OSPF, EIGRP
IPX	RIP, NLSP, EIGRP
Appletalk	RMTP, AURP, EIGRP

3.What is Autonomous System and Autonomous System Number

An Autonomous System (AS) is a group of networks under a single administrative control, which could be your company, a division within your company, or a group of companies. An Interior Gateway Protocol (IGP) refers to a routing protocol that handles routing within a single autonomous system. IGPs include RIP, IGRP, EIGRP, and OSPF. An Exterior Gateway Protocol (EGP) handles routing between different Autonomous Systems (AS). Border Gateway Protocol (BGP) is an EGP. BGP is used to route traffic across the Internet backbone between different autonomous systems.
Autonomous System Numbers are 16-bit numbers, allowing 65,536 possible values. The Autonomous System Number (ASN) value 0 is reserved, and the largest ASN value 65,535, is also reserved. The values, from 1 to 64,511, are available for use in Internet routing, and the values 64,512 to 65,534 is designated for private use. Routing protocols that understand the concept of an Autonomous System (AS) are IGRP, EIGRP, OSPF, IS-IS, and BGP.

4.What is Administrative Distance

Administrative Distance (AD) is a value that routers use in order to select the best path when there are two or more different routes to the same destination from two different routing protocols. Administrative Distance counts the reliability of a routing protocol. Administrative Distance (AD) is a numeric value which can range from 0 to 255. A smaller Administrative Distance (AD) is more trusted by a router, therefore the best Administrative Distance (AD) being 0 and the worst, 255.

Administrative Distance (AD)	Route Type
0	Connected interface
0 or 1	Static Route
90	Internal EIGRP Route (within the same AS)
100	IGRP Route
110	OSPF Route
115	IS-IS
120	RIP Route
255	Unknown Route

5.Introduction to Static Routes and Default Routes

What is a Static Route

A static route is a route that is created manually by a network administrator. Static routes are typically used in smaller networks. In static routing, the routing table entries are populated manually by a network administrator.
The opposite of a static route is a dynamic route. In dynamic routing, the the routing table entries are populated with the help of routing protocols.
The major advantages of static routing are reduced routing protocol router overhead and reduced routing protocol network traffic. The major disadvantages of static routing are network changes require manual reconfiguration in routers and network outages cannot be automatically routed around. Also it is difficult to configure static routing in a complex network.

What is a Default Route

A Default Route (also known as the gateway of last resort) is a special type of static route. Where a static route specifies a path a router should use to reach a specific destination, a default route specifies a path the router should use if it doesn’t know how to reach the destination.
Default Route is the network route used by a router when there is no other known route exists for a given IP datagram's destination address. All the IP datagrams with unknown destination address are sent to the default route.

6.How to configure Static Routes and Default Routes

How to configure Static Routes

Static Route can be configured by the following IOS commands.
• Router(config)#ip route destination_network subnet_mask default_gateway [administrative_distance] [permanent]
OR
• Router(config)# ip route destination_network subnet_mask interface_to_exit [administrative_distance] [permanent]
The permanent keyword will keep the static route in the routing table even when the interface the router uses for the static route fails.

Static Routing - Lab Practice

The following diagram shows our lab setup. We have three routers, three switches and three hosts connected as below. The host names, IP addresses and the interfaces of the routers are shown in diagram. The IP addresses of the hosts are also shown in the diagram.

If you are not familiar with a router console connection, click the following link to learn how to connect the serial port of your computer to router console port.
Click the following link to learn how to connect to the console port of the router if there is no serial port in your computer.
Click the following links to learn how to use HyperTerminal terminal emulator and PuTTY terminal emulator to configure router.

Hostname and IP address configuration in Router01

Connect to Router01 console and use the following IOS commands to configure host name as Router01.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router01
Router01(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router01 and configure IP address as 172.16.0.1/16.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface fa0/0
Router01(config-if)#ip address 172.16.0.1 255.255.0.0
Router01(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router01 and configure IP address as 172.17.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/0 interface, since this is the DCE side.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface s0/0
Router01(config-if)#clock rate 64000
Router01(config-if)#ip address 172.17.0.1 255.255.0.0
Router01(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router02

Connect to Router02 console and use the following IOS commands to configure host name as Router02.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router02
Router02(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router02 and configure IP address as 172.18.0.1/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface fa0/0
Router02(config-if)#ip address 172.18.0.1 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router02 and configure IP address as 172.17.0.2/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/0
Router02(config-if)#ip address 172.17.0.2 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router02 and configure IP address as 172.19.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/1 interface, since this is the DCE side.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/1
Router02(config-if)#clock rate 64000
Router02(config-if)#ip address 172.19.0.1 255.255.0.0
Router02(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router03

Connect to Router03 console and use the following IOS commands to configure host name as Router03.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router03
Router03(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router03 and configure IP address as 172.20.0.1/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface fa0/0
Router03(config-if)#ip address 172.20.0.1 255.255.0.0
Router03(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router03 and configure IP address as 172.19.0.2/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface s0/1
Router03(config-if)#ip address 172.19.0.2 255.255.0.0
Router03(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Static Routing configuration in Router01

Connect to Router01 console and use the following IOS commands to configure static routing in Router01. The "ip route" commands shown below states that to reach 172.18.0.0/16, 172.19.0.0/16 and 172.20.0.0/16 networks, handover the packets to the gateway ip address 172.17.0.2. The networks 172.16.0.0/16 and 172.17.0.0/16 are conneted directly to Router01.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#ip route 172.18.0.0 255.255.0.0 172.17.0.2
Router01(config)#ip route 172.19.0.0 255.255.0.0 172.17.0.2
Router01(config)#ip route 172.20.0.0 255.255.0.0 172.17.0.2

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router. To view the routing table in Router01, run "show ip route" command in Router01 as shown below.

Router01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

C 172.16.0.0/16 is directly connected, FastEthernet0/0
C 172.17.0.0/16 is directly connected, Serial0/0
S 172.18.0.0/16 [1/0] via 172.17.0.2
S 172.19.0.0/16 [1/0] via 172.17.0.2
S 172.20.0.0/16 [1/0] via 172.17.0.2

The "S" character at the beginning of a line in routing table shows that it is a static route and "C" character shows that it is a directly connected network.

Static Routing configuration in Router02

Connect to Router02 console and use the following IOS commands to configure static routing in Router02. The "ip route" commands shown below states that to reach 172.16.0.0/16 network, handover the packets to the gateway ip address 172.17.0.1 and to reach 172.20.0.0/16 network, handover the packets to the gateway ip address 172.19.0.2. The networks 172.17.0.0/16, 172.18.0.0/16 and 172.19.0.0/16 are connected directly to Router02.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#ip route 172.16.0.0 255.255.0.0 172.17.0.1
Router02(config)#ip route 172.20.0.0 255.255.0.0 172.19.0.2

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router. To view the routing table in Router02, run "show ip route" command in Router02 as shown below.

Router02#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

S 172.16.0.0/16 [1/0] via 172.17.0.1
C 172.17.0.0/16 is directly connected, Serial0/0
C 172.18.0.0/16 is directly connected, FastEthernet0/0
C 172.19.0.0/16 is directly connected, Serial0/1
S 172.20.0.0/16 [1/0] via 172.19.0.2

The "S" character at the beginning of a line in routing table shows that it is a static route and "C" character shows that it is a directly connected network.

Static Routing configuration in Router03

Connect to Router03 console and use the following IOS commands to configure static routing in Router03. The "ip route" commands shown below states that to reach 172.16.0.0/16, 172.17.0.0/16 and 172.18.0.0/16 networks, handover the packets to the gateway ip address 172.19.0.1. The networks 172.19.0.0/16 and 172.20.0.0/16 are conneted directly to Router03.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#ip route 172.16.0.0 255.255.0.0 172.19.0.1
Router03(config)#ip route 172.17.0.0 255.255.0.0 172.19.0.1
Router03(config)#ip route 172.18.0.0 255.255.0.0 172.19.0.1

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router. To view the routing table in Router03, run "show ip route" command in Router03 as shown below.

Router03#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

S 172.16.0.0/16 [1/0] via 172.19.0.1
S 172.17.0.0/16 [1/0] via 172.19.0.1
S 172.18.0.0/16 [1/0] via 172.19.0.1
C 172.19.0.0/16 is directly connected, Serial0/1
C 172.20.0.0/16 is directly connected, FastEthernet0/0

The "S" character at the beginning of a line in routing table shows that it is a static route and "C" character shows that it is a directly connected network.

Verify the connectivity between networks using the ping command

To verify the static routes which we have configured and the connectivity between networks, run the ping command from Host01 (IP address: 172.16.0.10/16) to Host03 (IP address: 172.20.0.10/16).

C:\>ping 172.20.0.10

Pinging 172.20.0.10 with 32 bytes of data:

Reply from 172.20.0.10: bytes=32 time=172ms TTL=125
Reply from 172.20.0.10: bytes=32 time=235ms TTL=125
Reply from 172.20.0.10: bytes=32 time=187ms TTL=125
Reply from 172.20.0.10: bytes=32 time=187ms TTL=125

Ping statistics for 172.20.0.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 172ms, Maximum = 235ms, Average = 195ms

The ping reply from Host03 (IP address: 172.20.0.10/16) shows that the static routes are configured well in three routers and there is network connectivity between different networks.

How to configure Default Routes

Default Route can be configured by the following IOS commands.
• Router(config)#ip route 0.0.0.0 0.0.0.0 default_gateway [administrative_distance] [permanent]
OR
• Router(config)# ip route 0.0.0.0 0.0.0.0 interface_to_exit [administrative_distance] [permanent]

7.What is Dynamic Routing and different types of Dynamic Routing

Static routing allows routing tables in specific routers to be set up by the network administrator. Dynamic routing use Routing Protocols that dynamically discover network destinations and how to get to them. Dynamic routing allows routing tables in routers to change if a router on the route goes down. Examples of Routing Protocols are RIP, EIGRP and OSPF.
There are three basic types of routing protocols.
Distance-vector Routing Protocols: Distance-vector Routing Protocols use simple algorithms that calculate a cumulative distance value between routers based on hop count.
Example: RIP
Link-state Routing Protocols: Link-state Routing Protocols use sophisticated algorithms that maintain a complex database of internetwork topology.
Example: OSPF
Hybrid Routing Protocols: Hybrid Routing Protocols use a combination of distance-vector and link-state methods that tries to incorporate the advantages of both and minimize their disadvantages.
Example: EIGRP

8.What is Routing Metric Value

If the router has two types of routes, for the same network, the router chooses Administrative Distance to choose the best one. But in some cases, there will be two paths found by the same protocol, to the destination network. Here the routing protocol will use routing metric value to find the best path.
Example: RIP (Routing Information Protocol) uses hop count as the metric.
Following are some of the factors to choose a best path to destination.

Metric	Routing Protocols	Description
Bandwidth	IP EIGRP, IP IGRP	The bandwidth of the links in Kbps (T1=1,554)
Cost	IP OSPF	Measurement in the inverse of the bandwidth of the links
Delay	IP EIGRP, IP IGRP	Time it takes to reach the destination
Hop count	IP RIP	How many routers away from the destination
Load	IP EIGRP, IP IGRP	The path with the least utilization
Reliability	IP EIGRP, IP IGRP	The path with the least amount of errors or downtime

If a router found multiple paths with the same administrative distance and metric to a destination, load balancing can occur. Cisco IOS Software has a limit of six equal-cost routes on the routing table, but some protocols set their own limitations. For example, EIGRP allows up to four equal-cost routes.

9.What is Convergence of Routing Tables

In dynamic routing, routing tables are created dynamically by obtaining the network information from other routers. Routers in the network must be constantly updated to changes in the network topology. Routes may be added or removed, or routes may fail due to a break in the physical link.
When a new link is added or a link fails or changes, updates are sent by routers across the network that describe changes in the network topology. Other routers in the network then runs a routing algorithm to recalculate routes and build new routing tables based on the update information.
After recalculation, all the routing tables have arrived at a common view of the network topology. A converged network topology view means all the routers agree on which links are up, which links are down, which links are running fastest etc.
Convergence time is the time which a group of routers reach the state of convergence. Optimally the routing protocols must have fast convergence time.

10.Introduction to Distance Vector Routing Protocols

Distance Vector protocols are the simplest amoung Routing Protocols. Distance vector routing protocols use the distance and direction (vector) to find paths to destinations. Distance Vector protocols use the Bellman-Ford algorithm for finding paths to destinations.
Routers running Distance Vector protocols learn who their neighbours are by listening for routing broadcasts on their interfaces. Distance Vector protocols periodically send local broadcasts (255.255.255.255) to share routing information.
Distance Vector algorithms pass routing table updates to their immediate neighbors in all directions. At each exchange, the router increments the distance value received for a route, thereby applying its own distance value to it. The routerwho received this update again pass the updated table further outward, where receiving routers repeat the process.
The Distance Vector protocols do not check who is listening to the updates which they sent and Distance Vector protocols broadcast the updates periodically even if there is no change in the network topology.
Distance Vector protocols are the simplest among three types of dynamic routing protocols. They are easy to set-up and troubleshoot. They require less router resources. They receive the routing update, increment the metric, compare the result to the routes in the routing table, and update the routing table if necessary

11.Introduction to Routing Information Protocol (RIP)

IP RIP (Routing Information Protocol) comes in two different versions: 1 and 2. Version 1 is a distance vector protocol (RFC 1058) and Version 2 is a hybrid protocol (RFCs 1721 and 1722).

Routing Information Protocol Version 1 (RIPv1)

RIPv1 uses local broadcasts to share routing information. These updates are periodic in nature, occurring, by default, every 30 seconds. To prevent packets from circling around a loop forever, both versions of RIP solve counting to infinity by placing a hop count limit of 15 hops on packets. Any packet that reaches the sixteenth hop will be dropped. RIPv1 is a classful protocol. RIP supports up to six equal-cost paths to a single destination. Equal-cost path are the paths where the metric is same (Hop count).

Routing Information Protocol (RIPv2)

RIPv2 is a distance vector protocol with routing enhancements built into it, and it is based on RIPV1. Therefore, it is commonly called a hybrid protocol.
RIPv2 uses multicasts instead of broadcasts. RIPv2 supports triggered updates. when a change occurs, a RIPv2 router will immediately propagate its routing information to its connected neighbours. RIPv2 is a classless protocol and it supports variable-length subnet masking (VLSM).
Both RIPv1 and RIPv2 uses hop count as the metric.

Differences between RIPv1 and RIPv2

RIPv1

• Supports only classful routing (Does not support VLSM).
• No authentication.
• RIPv1 uses Broadcast.

RIPv2

• Supports classless routing (Supports VLSM). RIPv2 incorporates the addition of the network mask in the update to allow classless routing advertisements.
• Authentication is available.
• RIPv2 uses multi-cast instead of broadcast. multicast communication reduces the burden on the network devices that do not need to listen to RIP updates.

11.How to configure Routing Information Protocol (RIP)

If you are not familiar with Routing Information Protocol (RIP), click the following link to view an introduction to Routing Information Protocol (RIP).

Routing Information Protocol (RIP) Configuration

Routing Information Protocol (RIP) can be configured in a router using the following IOS commands. The "version 2" IOS command specifies that we are using RIPv2.

Router>enable
Router#configure terminal
Router(config)# router rip
Router(config-router)# version 2
Router(config-router)# network network_id

Routing Information Protocol (RIP) - Lab Practice

The following diagram shows our lab setup. We have three routers, three switches and three hosts connected as below. The host names, IP addresses and the interfaces of the routers are shown in diagram. The IP addresses of the hosts are also shown in the diagram.



If you are not familiar with a router console connection, click the following link to learn how to connect the serial port of your computer to router console port.
Click the following link to learn how to connect to the console port of the router if there is no serial port in your computer.
Click the following links to learn how to use HyperTerminal terminal emulator and PuTTY terminal emulator to configure router.

Hostname and IP address configuration in Router01

Connect to Router01 console and use the following IOS commands to configure host name as Router01.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router01
Router01(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router01 and configure IP address as 172.16.0.1/16.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface fa0/0
Router01(config-if)#ip address 172.16.0.1 255.255.0.0
Router01(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router01 and configure IP address as 172.17.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/0 interface, since this is the DCE side.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface s0/0
Router01(config-if)#clock rate 64000
Router01(config-if)#ip address 172.17.0.1 255.255.0.0
Router01(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router02

Connect to Router02 console and use the following IOS commands to configure host name as Router02.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router02
Router02(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router02 and configure IP address as 172.18.0.1/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface fa0/0
Router02(config-if)#ip address 172.18.0.1 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router02 and configure IP address as 172.17.0.2/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/0
Router02(config-if)#ip address 172.17.0.2 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router02 and configure IP address as 172.19.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/1 interface, since this is the DCE side.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/1
Router02(config-if)#clock rate 64000
Router02(config-if)#ip address 172.19.0.1 255.255.0.0
Router02(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router03

Connect to Router03 console and use the following IOS commands to configure host name as Router03.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router03
Router03(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router03 and configure IP address as 172.20.0.1/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface fa0/0
Router03(config-if)#ip address 172.20.0.1 255.255.0.0
Router03(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router03 and configure IP address as 172.19.0.2/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface s0/1
Router03(config-if)#ip address 172.19.0.2 255.255.0.0
Router03(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Routing Information Protocol Version 2 (RIPv2) configuration in Router01

Connect to Router01 console and use the following IOS commands to configure Routing Information Protocol Version 2 (RIPv2) in Router01. Please refer the beginning of this lesson to view the Routing Information Protocol Version 2 (RIPv2) configuration IOS commands.
Using the IOS "network" command, as shown below, we specify only the directly connected networks of this router.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#router rip
Router01(config-router)#version 2
Router01(config-router)#network 172.16.0.0
Router01(config-router)#network 172.17.0.0
Router01(config-router)#exit
Router01(config)#exit
Router01#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Routing Information Protocol Version 2 (RIPv2) configuration in Router02

Connect to Router02 console and use the following IOS commands to configure Routing Information Protocol Version 2 (RIPv2) in Router02. Please refer the beginning of this lesson to view the Routing Information Protocol Version 2 (RIPv2) configuration IOS commands.
Using the IOS "network" command, as shown below, we specify only the directly connected networks of this router.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#router rip
Router02(config-router)#version 2
Router02(config-router)#network 172.17.0.0
Router02(config-router)#network 172.18.0.0
Router02(config-router)#network 172.19.0.0
Router02(config-router)#exit
Router02(config)#exit
Router02#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Routing Information Protocol Version 2 (RIPv2) configuration in Router03

Connect to Router03 console and use the following IOS commands to configure Routing Information Protocol Version 2 (RIPv2) in Router03. Please refer the beginning of this lesson to view the Routing Information Protocol Version 2 (RIPv2) configuration IOS commands.
Using the IOS "network" command, as shown below, we specify only the directly connected networks of this router.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#router rip
Router03(config-router)#version 2
Router03(config-router)#network 172.19.0.0
Router03(config-router)#network 172.20.0.0
Router03(config-router)#exit
Router03(config)#exit
Router03#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

How to view the routing table in Router01

After the network is converged after the initial configuration and Routing Information Protocol Version 2 (RIPv2) configuration, we can use the "show ip route" to view the routing table in Router01, as shown below.

Router01>enable
Router01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

C 172.16.0.0/16 is directly connected, FastEthernet0/0
C 172.17.0.0/16 is directly connected, Serial0/0
R 172.18.0.0/16 [120/1] via 172.17.0.2, 00:00:22, Serial0/0
R 172.19.0.0/16 [120/1] via 172.17.0.2, 00:00:22, Serial0/0
R 172.20.0.0/16 [120/2] via 172.17.0.2, 00:00:22, Serial0/0

The "R" character at the beginning of a line in routing table shows that it is a route discovered by Routing Information Protocol Version 2 (RIPv2) and "C" character shows that it is a directly connected network.

How to view the routing table in Router02

When the network is converged after the initial configuration and Routing Information Protocol Version 2 (RIPv2) configuration, we can use the "show ip route" to view the routing table in Router02, as shown below.

Router02>enable
Router02#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

R 172.16.0.0/16 [120/1] via 172.17.0.1, 00:00:07, Serial0/0
C 172.17.0.0/16 is directly connected, Serial0/0
C 172.18.0.0/16 is directly connected, FastEthernet0/0
C 172.19.0.0/16 is directly connected, Serial0/1
R 172.20.0.0/16 [120/1] via 172.19.0.2, 00:00:20, Serial0/1

The "R" character at the beginning of a line in routing table shows that it is a route discovered by Routing Information Protocol Version 2 (RIPv2) and "C" character shows that it is a directly connected network.

How to view the routing table in Router03

When the network is converged after the initial configuration and Routing Information Protocol Version 2 (RIPv2) configuration, we can use the "show ip route" to view the routing table in Router03, as shown below.

Router03>enable
Router03#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

R 172.16.0.0/16 [120/2] via 172.19.0.1, 00:00:02, Serial0/1
R 172.17.0.0/16 [120/1] via 172.19.0.1, 00:00:02, Serial0/1
R 172.18.0.0/16 [120/1] via 172.19.0.1, 00:00:02, Serial0/1
C 172.19.0.0/16 is directly connected, Serial0/1
C 172.20.0.0/16 is directly connected, FastEthernet0/0

The "R" character at the beginning of a line in routing table shows that it is a route discovered by Routing Information Protocol Version 2 (RIPv2) and "C" character shows that it is a directly connected network.

Verify the connectivity between networks using the ping command

To verify the Routing Information Protocol Version 2 (RIPv2) routes and the connectivity between networks, run the ping command from Host01 (IP address: 172.16.0.10/16) to Host03 (IP address: 172.20.0.10/16).

C:\>ping 172.20.0.10

Pinging 172.20.0.10 with 32 bytes of data:

Reply from 172.20.0.10: bytes=32 time=172ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125
Reply from 172.20.0.10: bytes=32 time=157ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125

Ping statistics for 172.20.0.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 157ms, Maximum = 188ms, Average = 176ms

The ping reply from Host03 (IP address: 172.20.0.10/16) shows that the Routing Information Protocol Version 2 (RIPv2) is configured well in three routers and there is network connectivity between different networks.

12.Introduction to Interior Gateway Routing Protocol (IGRP)

The Interior Gateway Routing Protocol (IGRP) is a Cisco-proprietary routing protocol for IP.
Some of the features ifInterior Gateway Routing Protocol (IGRP) are
• Interior Gateway Routing Protocol (IGRP) uses a sophisticated metric based on bandwidth and delay.
• Interior Gateway Routing Protocol (IGRP) uses triggered updates to speed-up convergence.
• Interior Gateway Routing Protocol (IGRP) supports unequal-cost load balancing to a single destination.
Interior Gateway Routing Protocol (IGRP) uses bandwidth, delay, reliability, load, to find the metric value. By default, the algorithm uses only bandwidth and delay, but the other metric components can be enabled. IGRP uses bandwidth, delay, reliability, load, and MTU to find the metric value. By default, the algorithm uses only bandwidth and delay, but the other metric components can be enabled.
The following formula is used to calculate the composite metric of IGRP.
Metric = [K1 * Bandwidth + (K2 * Bandwidth)/ (256-Load) + K3*Delay] * [K5/(Reliability + K4)]
The default constant values are K1 = K3 = 1 and K2 = K4 = K5 = 0.
If K5 = 0, the [K5/ (reliability + K4)] term is not used. So, given the default values for K1 through K5, the composite metric calculation used by IGRP reduces to Metric = Bandwidth + Delay.
• To find the bandwidth value, find the smallest of all the bandwidths in Kbps from outgoing interfaces and divide 10,000,000 by that number.
• Reliability and load are measured 1–255. A reliability of 1 is least reliable, while 255 is most reliable. A load of 1 is least utilized, while 255 is 100 percent utilized. The MTU refers to the size of the frame. If a route has lower metric value, then that route is preferred.
• In order to find the delay, add all of the delays (in microseconds) from the outgoing interfaces and divide this number by 10. (The delay is in tenths of microseconds.)

13.How to configure Interior Gateway Routing Protocol (IGRP)

 If you are not familiar with Interior Gateway Routing Protocol (IGRP), click the following link to view an introduction to Interior Gateway Routing Protocol (IGRP).

Interior Gateway Routing Protocol (IGRP) Configuration

Interior Gateway Routing Protocol (IGRP) can be configured in a router using the following IOS commands. If you have a new router with a latest IOS release, you may not find Interior Gateway Routing Protocol (IGRP) configuration commands because Interior Gateway Routing Protocol (IGRP) is removed from new IOS releases.

Router(config)# router igrp ASN
Router(config-router)# network Network_ID

ASN in the above IOS command stands for Autonomous System Number.

Interior Gateway Routing Protocol (IGRP) - Lab Practice

The following diagram shows our lab setup. We have three routers, three switches and three hosts connected as below. The host names, IP addresses and the interfaces of the routers are shown in diagram. The IP addresses of the hosts are also shown in the diagram.

If you are not familiar with a router console connection, click the following link to learn how to connect the serial port of your computer to router console port.
Click the following link to learn how to connect to the console port of the router if there is no serial port in your computer.
Click the following links to learn how to use HyperTerminal terminal emulator and PuTTY terminal emulator to configure router.

Hostname and IP address configuration in Router01

Connect to Router01 console and use the following IOS commands to configure host name as Router01.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router01
Router01(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router01 and configure IP address as 172.16.0.1/16.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface fa0/0
Router01(config-if)#ip address 172.16.0.1 255.255.0.0
Router01(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router01 and configure IP address as 172.17.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/0 interface, since this is the DCE side.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface s0/0
Router01(config-if)#clock rate 64000
Router01(config-if)#ip address 172.17.0.1 255.255.0.0
Router01(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router02

Connect to Router02 console and use the following IOS commands to configure host name as Router02.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router02
Router02(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router02 and configure IP address as 172.18.0.1/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface fa0/0
Router02(config-if)#ip address 172.18.0.1 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router02 and configure IP address as 172.17.0.2/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/0
Router02(config-if)#ip address 172.17.0.2 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router02 and configure IP address as 172.19.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/1 interface, since this is the DCE side.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/1
Router02(config-if)#clock rate 64000
Router02(config-if)#ip address 172.19.0.1 255.255.0.0
Router02(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router03

Connect to Router03 console and use the following IOS commands to configure host name as Router03.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router03
Router03(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router03 and configure IP address as 172.20.0.1/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface fa0/0
Router03(config-if)#ip address 172.20.0.1 255.255.0.0
Router03(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router03 and configure IP address as 172.19.0.2/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface s0/1
Router03(config-if)#ip address 172.19.0.2 255.255.0.0
Router03(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Interior Gateway Routing Protocol (IGRP) configuration in Router01

Connect to Router01 console and use the following IOS commands to configure Interior Gateway Routing Protocol (IGRP) in Router01. Please refer the beginning of this lesson to view the Interior Gateway Routing Protocol (IGRP) configuration IOS command.
In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)# router igrp 1
Router01(config-router)# network 172.16.0.0
Router01(config-router)# network 172.17.0.0
Router01(config-router)#exit
Router01(config)#exit
Router01#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Interior Gateway Routing Protocol (IGRP) configuration in Router02

Connect to Router02 console and use the following IOS commands to configure Interior Gateway Routing Protocol (IGRP) in Router02. Please refer the beginning of this lesson to view the Interior Gateway Routing Protocol (IGRP) configuration IOS command.
In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)# router igrp 1
Router02(config-router)# network 172.17.0.0
Router02(config-router)# network 172.18.0.0
Router02(config-router)# network 172.19.0.0
Router02(config-router)#exit
Router02(config)#exit
Router02#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Interior Gateway Routing Protocol (IGRP) configuration in Router03

Connect to Router03 console and use the following IOS commands to configure Interior Gateway Routing Protocol (IGRP) in Router03. Please refer the beginning of this lesson to view the Interior Gateway Routing Protocol (IGRP) configuration IOS command.
In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)# router igrp 1
Router03(config-router)# network 172.19.0.0
Router03(config-router)# network 172.20.0.0
Router03(config-router)#exit
Router03(config)#exit
Router03#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

How to view the routing table in Router01

After the network is converged after the initial configuration and Interior Gateway Routing Protocol (IGRP) configuration, we can use the "show ip route" to view the routing table in Router01, as shown below.

Router01>enable
Router01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

C 172.16.0.0/16 is directly connected, FastEthernet0/0
C 172.17.0.0/16 is directly connected, Serial0/0
I 172.18.0.0/16 [120/1] via 172.17.0.2, 00:00:22, Serial0/0
I 172.19.0.0/16 [120/1] via 172.17.0.2, 00:00:22, Serial0/0
I 172.20.0.0/16 [120/2] via 172.17.0.2, 00:00:22, Serial0/0

The "I" character at the beginning of a line in routing table shows that it is a route discovered byInterior Gateway Routing Protocol (IGRP) and "C" character shows that it is a directly connected network.

How to view the routing table in Router02

When the network is converged after the initial configuration and Interior Gateway Routing Protocol (IGRP) configuration, we can use the "show ip route" to view the routing table in Router02, as shown below.

Router02>enable
Router02#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

I 172.16.0.0/16 [120/1] via 172.17.0.1, 00:00:07, Serial0/0
C 172.17.0.0/16 is directly connected, Serial0/0
C 172.18.0.0/16 is directly connected, FastEthernet0/0
C 172.19.0.0/16 is directly connected, Serial0/1
I 172.20.0.0/16 [120/1] via 172.19.0.2, 00:00:20, Serial0/1

The "I" character at the beginning of a line in routing table shows that it is a route discovered by Interior Gateway Routing Protocol (IGRP) and "C" character shows that it is a directly connected network.

How to view the routing table in Router03

When the network is converged after the initial configuration and Interior Gateway Routing Protocol (IGRP) configuration, we can use the "show ip route" to view the routing table in Router03, as shown below.

Router03>enable
Router03#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

I 172.16.0.0/16 [120/2] via 172.19.0.1, 00:00:02, Serial0/1
I 172.17.0.0/16 [120/1] via 172.19.0.1, 00:00:02, Serial0/1
I 172.18.0.0/16 [120/1] via 172.19.0.1, 00:00:02, Serial0/1
C 172.19.0.0/16 is directly connected, Serial0/1
C 172.20.0.0/16 is directly connected, FastEthernet0/0

The "I" character at the beginning of a line in routing table shows that it is a route discovered by Interior Gateway Routing Protocol (IGRP) and "C" character shows that it is a directly connected network.

Verify the connectivity between networks using the ping command

To verify the Interior Gateway Routing Protocol (IGRP) routes and the connectivity between networks, run the ping command from Host01 (IP address: 172.16.0.10/16) to Host03 (IP address: 172.20.0.10/16).

C:\>ping 172.20.0.10

Pinging 172.20.0.10 with 32 bytes of data:

Reply from 172.20.0.10: bytes=32 time=172ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125
Reply from 172.20.0.10: bytes=32 time=157ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125

Ping statistics for 172.20.0.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 157ms, Maximum = 188ms, Average = 176ms

The ping reply from Host03 (IP address: 172.20.0.10/16) shows that the Interior Gateway Routing Protocol (IGRP) is configured well in three routers and there is network connectivity between different networks

14.What is Routing Loop and how to avoid Routing Loop

A routing loop is a serious network problem which happens when a data packet is continually routed through the same routers over and over. The data packets continue to be routed within the network in an endless circle. A routing loop can have a catastrophic impact on a network, and in some cases, completely disabling the network. Normally Routing Loop is a problem associated with Distance Vector Protocols.
Routing Loop can happen in large internetworks when a second topology change emerges before the network is able to converge on the first change. Convergence is the term used to describe the condition when all routers in an internetwork have agreed on a common topology. Link state protocols tend to converge very quickly, while distance vector protocols tend to converge slowly.
The following methods are used to avoid Routing Loops.

Maximum hop Count

Maximum hop count mechanism can be used to prevent Routing Loops. Distance Vector protocols use the TTL (Time-to-Live) value in the IP datagram header to avoid Routing Loops. When an IP datagram move from router to router, a router keeps track of the hops in the TTL field in the IP datagram header. For each hop a packet goes through, the packet’s TTL field is decremented by one. If this value reaches 0, the packet is dropped by the router that decremented the value from 1 to 0.

Split Horizon

A split horizon is a routing configuration that stops a route from being advertised back in the direction from which it came. Split Horizon mechanism states that if a neighbouring router sends a route to a router, the receiving router will not propagate this route back to the advertising router on the same interface.

Route Poisoning

Route Poisoning is another method for avoiding routing loops. When a router detects that one of its connected routes has failed, the router will poison the route by assigning an infinite metric to it.

Hold-down Timers

Hold-down timer is another mechanism used to prevent bad routes from being restored and propagated by mistake. When a route is placed in a hold-down state, routers will neither advertise the route nor accept advertisements about it for a specific interval called the hold-down period

15.Introduction to Link State Routing Protocols

Link state protocols are based on Shortest Path First (SPF) algorithm to find the best path to a destination. Shortest Path First (SPF) algorithm is also known as Dijkstra algorithm, since it is conceptualized by Dijkstra. In Shortest Path First (SPF) algorithm, whenever a link's state changes, a routing update called a Link-State Advertisement (LSA) is exchanged between routers.  When a router receives an LSA routing update, the link-state algorithm is used to recalculate the shortest path to affected destinations.  Link-state routing always try to maintain full networks topology by updating itself incrementally whenever a change happen in network. Each router constructs a map of the complete network. An example of Link State protocol is OSPF (Open Shortest Path First).
Some important terms related with Link State Routing Protocols
• Link-state advertisements (LSAs) – A link-state advertisement (LSA) is a small packet of routing information that is sent between routers.
• Topological database – A topological database is a collection of information gathered from LSAs.
• SPF algorithm (Dijkstra algorithm) – The shortest path first (SPF) algorithm is a calculation performed on the database resulting in the SPF tree.
• Routing tables – A list of the known paths and interfaces.
Link State Routing Protocols converge more quickly and they are less prone to routing loops than Distance Vector algorithms. On the other hand, Link State Routing Protocols require more CPU power and memory than distance vector algorithms. Link State Protocols use a hierarchical structure that limits the distance that a Link-State Advertisement (LSA) need to travel. Link State Protocols use multicasts to share the routing information. Only the routers which run Link State protocol only process the updates. Link State routers send updates only when there is a change in the state of the network (incremental updates).
Link-state algorithms can be more complex and expensive to implement and support.

16.Introduction to Open Shortest Path First (OSPF) Protocol

The Open Shortest Path First (OSPF) protocol is a link state protocol that handles routing for IP traffic. Its newest implementation, version 2, which is explained in RFC 2328, is an open standard. Open Shortest Path First (OSPF) is an open standard (not proprietary) and it will run on most routers independent of make. Open Shortest Path First (OSPF) uses the Shortest Path First (SPF) algorithm, developed by Dijkstra, to provide a loop-free topology. Open Shortest Path First (OSPF) provides fast convergence with triggered, incremental updates via Link State Advertisements (LSAs). Open Shortest Path First (OSPF) is a classless protocol and allows for a hierarchical design with VLSM and route summarization
The main disadvantages of Open Shortest Path First (OSPF) are Open Shortest Path First (OSPF) requires more memory to hold the adjacency (list of OSPF neighbors), topology (a link state database containing all of the routers and their routes), and routing tables, Open Shortest Path First (OSPF) requires extra CPU processing to run the SPF algorithm and Open Shortest Path First (OSPF) is a complex routing protocol.
The two important concepts in case of OSPF are Autonomous Systems and Areas. Areas are used to provide hierarchical routing, within an Autonomous System. Areas are used to control when and how much routing information is shared across your network.
OSPF implements a two-layer hierarchy: the backbone (Area 0) and areas off of the backbone (Areas 1–65,535). Here the two different areas can summarize routing information between them. Route summerization helps to compact the routing tables. All areas should connect to Area 0 and all routers in an Area will have the same topology table.

Open Shortest Path First (OSPF) metric value

Open Shortest Path First (OSPF) uses cost as the value of metric and uses a reference bandwidth of 100 Mbps for cost calculation. The formula to calculate the cost is reference bandwidth divided by interface bandwidth. For example, in the case of Ethernet, it is 100 Mbps / 10 Mbps = 10.

Important Terms related with Open Shortest Path First (OSPF)

Router ID

Each router in an OSPF network needs a unique ID. The ID is used to provide a unique identity to the OSPF router.
• The highest IP address on its loopback interfaces (this is a logical interface on a router)
• The highest IP address on its active interfaces

What is a Loopback Interface

A loopback interface is a logical, virtual interface on a router. By default, the router doesn’t have any loopback interfaces, but they can easily be created. These interfaces are treated as physical interfaces on a router and we can assign ip addresses to them.

Router(Config)#int loopback 2
Router(Config-if)#ip address 200.0.0.10 255.255.255.0

Area border router (ABR)

An Area border router (ABR) is a router that connects one or more OSPF areas to the main backbone network. It is considered a member of all areas it is connected to.

Internal router

An Internal Router is a router that has only OSPF neighbour relationships with routers in the same area.

Backbone router

Backbone Routers are part of the OSPF backbone. This includes all area border routers and also routers connecting different areas.

Designated Router (DR) and Backup Designated Router (BDR)

A Designated Router (DR) is the router interface elected among all routers on a network segment, and Backup designated (BDR) is a backup for the Designated Router (DR). Designated Routers (DRs) are used for reducing network traffic by providing a source for routing updates. The Designated Router (DR) maintains a complete topology table of the network and sends the updates to the other routers via multicast. All routers in an area will form a slave/master relationship with the Designated Router (DR).

16.How to configure Open Shortest Path First (OSPF) Protocol

If you are not familair with Open Shortest Path First (OSPF) Protocol click the following link to view an introduction to Open Shortest Path First (OSPF) Protocol.

Open Shortest Path First (OSPF) Protocol Configuration

Router(config)# router ospf process_ID
Router(config-router)# network network_id wildcard_mask area area_#

Note:
Process id: A value in the range 1–65,535 identifies the OSPF Process ID. OSPF Process ID is a unique number on this router that groups a series of OSPF configuration commands under a specific running process.
Wildcard Mask: The wildcard mask (wildcard_mask) given above is the inverse mask of the subnet mask. A 0 octet in the wildcard mask indicates that the corresponding octet in the network must match exactly. On the other hand, a 255 indicates that you don’t care what the corresponding octet is in the network number. A network and wildcard mask combination of 192.168.10.0 0.0.0.0 would match 192.168.10.0 only, and nothing else.
Area Number: The area_# given above is the Area Number. Area Number can always be zero (0) for small networks, but for larger networks, the Area Number need to be properly planned as all routing updates must traverse Area 0.

Open Shortest Path First (OSPF) Protocol - Lab Practice

The following diagram shows our lab setup. We have three routers, three switches and three hosts connected as below. The host names, IP addresses and the interfaces of the routers are shown in diagram. The IP addresses of the hosts are also shown in the diagram.

If you are not familiar with a router console connection, click the following link to learn how to connect the serial port of your computer to router console port.
Click the following link to learn how to connect to the console port of the router if there is no serial port in your computer.
Click the following links to learn how to use HyperTerminal terminal emulator and PuTTY terminal emulator to configure router.

Hostname and IP address configuration in Router01

Connect to Router01 console and use the following IOS commands to configure host name as Router01.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router01
Router01(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router01 and configure IP address as 172.16.0.1/16.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface fa0/0
Router01(config-if)#ip address 172.16.0.1 255.255.0.0
Router01(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router01 and configure IP address as 172.17.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/0 interface, since this is the DCE side.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface s0/0
Router01(config-if)#clock rate 64000
Router01(config-if)#ip address 172.17.0.1 255.255.0.0
Router01(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router02

Connect to Router02 console and use the following IOS commands to configure host name as Router02.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router02
Router02(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router02 and configure IP address as 172.18.0.1/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface fa0/0
Router02(config-if)#ip address 172.18.0.1 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router02 and configure IP address as 172.17.0.2/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/0
Router02(config-if)#ip address 172.17.0.2 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router02 and configure IP address as 172.19.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/1 interface, since this is the DCE side.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/1
Router02(config-if)#clock rate 64000
Router02(config-if)#ip address 172.19.0.1 255.255.0.0
Router02(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router03

Connect to Router03 console and use the following IOS commands to configure host name as Router03.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router03
Router03(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router03 and configure IP address as 172.20.0.1/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface fa0/0
Router03(config-if)#ip address 172.20.0.1 255.255.0.0
Router03(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router03 and configure IP address as 172.19.0.2/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface s0/1
Router03(config-if)#ip address 172.19.0.2 255.255.0.0
Router03(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Open Shortest Path First (OSPF) Protocol configuration in Router01

Connect to Router01 console and use the following IOS commands to configure Open Shortest Path First (OSPF) Protocol in Router01. Please refer the beginning of this lesson to view the Open Shortest Path First (OSPF) Protocol configuration IOS commands.
Using the IOS "network" command, as shown below, we specify only the directly connected networks of this router.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#router ospf 1
Router01(config-router)#network 172.16.0.0 0.0.255.255 area 0
Router01(config-router)#network 172.17.0.0 0.0.255.255 area 0
Router01(config-router)#exit
Router01(config)#exit
Router01#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Open Shortest Path First (OSPF) Protocol configuration in Router02

Connect to Router02 console and use the following IOS commands to configure Open Shortest Path First (OSPF) Protocol in Router02. Please refer the beginning of this lesson to view the Open Shortest Path First (OSPF) Protocol configuration IOS commands.
Using the IOS "network" command, as shown below, we specify only the directly connected networks of this router.
Router02>
Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#router ospf 1
Router02(config-router)#network 172.17.0.0 0.0.255.255 area 0
Router02(config-router)#network 172.18.0.0 0.0.255.255 area 0
Router02(config-router)#network 172.19.0.0 0.0.255.255 area 0
Router02(config-router)#exit
Router02(config)#exit
Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Open Shortest Path First (OSPF) Protocol configuration in Router03

Connect to Router03 console and use the following IOS commands to configure Open Shortest Path First (OSPF) Protocol in Router03. Please refer the beginning of this lesson to view the Open Shortest Path First (OSPF) Protocol configuration IOS commands.
Using the IOS "network" command, as shown below, we specify only the directly connected networks of this router.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#router ospf 1
Router03(config-router)#network 172.19.0.0 0.0.255.255 area 0
Router03(config-router)#network 172.20.0.0 0.0.255.255 area 0
Router03(config-router)#exit
Router03(config)#exit
Router03#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

How to view the routing table in Router01

After the initial configuration and Open Shortest Path First (OSPF) Protocol configuration in all routers, we can use the "show ip route" to view the routing table in Router01, as shown below.

Router01>enable
Router01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

C 172.16.0.0/16 is directly connected, FastEthernet0/0
C 172.17.0.0/16 is directly connected, Serial0/0
O 172.18.0.0/16 [110/65] via 172.17.0.2, 00:26:31, Serial0/0
O 172.19.0.0/16 [110/128] via 172.17.0.2, 00:26:21, Serial0/0
O 172.20.0.0/16 [110/129] via 172.17.0.2, 00:24:54, Serial0/0

The "O" character at the beginning of a line in routing table shows that it is a route discovered by Open Shortest Path First (OSPF) Protocol and "C" character shows that it is a directly connected network.

How to view the routing table in Router02

After the initial configuration and Open Shortest Path First (OSPF) Protocol configuration in all routers, we can use the "show ip route" to view the routing table in Router02, as shown below.

Router02>enable
Router02#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

O 172.16.0.0/16 [110/65] via 172.17.0.1, 00:30:20, Serial0/0
C 172.17.0.0/16 is directly connected, Serial0/0
C 172.18.0.0/16 is directly connected, FastEthernet0/0
C 172.19.0.0/16 is directly connected, Serial0/1
O 172.20.0.0/16 [110/65] via 172.19.0.2, 00:28:08, Serial0/1

The "O" character at the beginning of a line in routing table shows that it is a route discovered by Open Shortest Path First (OSPF) Protocol and "C" character shows that it is a directly connected network.

How to view the routing table in Router03

After the initial configuration and Open Shortest Path First (OSPF) Protocol configuration in all routers, we can use the "show ip route" to view the routing table in Router03, as shown below.

Router03>enable
Router03#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

O 172.16.0.0/16 [110/129] via 172.19.0.1, 00:29:43, Serial0/1
O 172.17.0.0/16 [110/128] via 172.19.0.1, 00:29:43, Serial0/1
O 172.18.0.0/16 [110/65] via 172.19.0.1, 00:29:43, Serial0/1
C 172.19.0.0/16 is directly connected, Serial0/1
C 172.20.0.0/16 is directly connected, FastEthernet0/0

The "O" character at the beginning of a line in routing table shows that it is a route discovered by Open Shortest Path First (OSPF) Protocol and "C" character shows that it is a directly connected network.

Verify the connectivity between networks using the ping command

To verify the Open Shortest Path First (OSPF) Protocol routes and the connectivity between networks, run the ping command from Host01 (IP address: 172.16.0.10/16) to Host03 (IP address: 172.20.0.10/16).

C:\>ping 172.20.0.10

Pinging 172.20.0.10 with 32 bytes of data:

Reply from 172.20.0.10: bytes=32 time=172ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125
Reply from 172.20.0.10: bytes=32 time=157ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125

Ping statistics for 172.20.0.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 157ms, Maximum = 188ms, Average = 176ms

The ping reply from Host03 (IP address: 172.20.0.10/16) shows that the Open Shortest Path First (OSPF) Protocol is configured well in three routers and there is network connectivity between different networks.

18.Introduction to Hybrid Routing Protocols

A hybrid protocol has the advantages of both distance vector and link state protocols and merges them into a new protocol. Typically, hybrid protocols are based on a distance vector protocol but contain many of the features and advantages of link state protocols. Example: EIGRP (Enhanced Interior Gateway Routing Protocol).
Enhanced Interior Gateway Routing Protocol (EIGRP) is considered as a Hybrid Routing Protocol because EIGRP has characteristics of both Distance Vector and Link State Routing Protocols. Enhanced Interior Gateway Routing Protocol (EIGRP) doesn’t send Link State Advertisement (LSA) packets as OSPF does, but Enhanced Interior Gateway Routing Protocol (EIGRP) sends traditional Distance Vector updates containing information about networks plus the cost of reaching them from the perspective of the advertising router. Enhanced Interior Gateway Routing Protocol (EIGRP) has link-state characteristics also. Enhanced Interior Gateway Routing Protocol (EIGRP) synchronizes routing tables between neighbors at startup, and then it sends specific updates when a network topology change happen.

19.Introduction to Enhanced Interior Gateway Routing Protocol (EIGRP)

Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary enhanced Distance Vector routing protocol. EIGRP is based on IGRP, hence the configuration is similar. Enhanced Interior Gateway Routing Protocol (EIGRP) is considered as a Hybrid Routing Protocol because EIGRP has characteristics of both Distance Vector and Link State Routing Protocols. Both EIGRP and IGRP offer load balancing across six paths (equal or unequal), and they have similar metric structures. EIGRP has faster convergence, and has less network overhead, since it uses incremental updates. Another important features of Enhanced Interior Gateway Routing Protocol (EIGRP) are routing loop-free topology, VLSM and route summarization, multicast and incremental updates and routes for multiple routed protocols (IP, IPX and AppleTalk)
Enhanced Interior Gateway Routing Protocol (EIGRP) Uses Diffused Update Algorithm (DUAL) to calculate the shortest path.

The following formula is used to calculate the metric of Enhanced Interior Gateway Routing Protocol (EIGRP).
Metric = [K1*Bandwidth + (K2*Bandwidth)/ (256 - Load) + K3*Delay] * [K5/(Reliability + K4)]
The default values for K are K1 = 1, K2 = 0, K3 = 1, K4 = 0, K5 = 0. For default behaviour, the formula can be simplified as metric = bandwidth + delay

Important terms related with Enhanced Interior Gateway Routing Protocol (EIGRP)

DUAL

DUAL stands for Diffused Update Algorithm, the algorithm used by Enhanced Interior Gateway Routing Protocol (EIGRP) to calculate the shortest path.

Neighbor table

Neighbor table contains a list of the EIGRP neighbours. Each routed protocol for EIGRP has its own neighbour table.

Topology table

Topology table contains a list of all destinations and paths the EIGRP router learned. There is a separate topology table for each routed protocol.

Successor

Successor is the best path to reach a destination within the topology table.

Feasible successor

Feasible successor is the best backup path to reach a destination

Routing table

Routing table contains all of the successor routes from the topology table. There is a separate routing table for each routed protocol.

Advertised distance

Advertised distance is the distance (metric) that a neighbouring router is advertising for a specific route.

Feasible distance

Feasible distance is the distance (metric) that your router will use to reach a specific route.

20.How to configure Enhanced Interior Gateway Routing Protocol (EIGRP)

If you are not familiar with Enhanced Interior Gateway Routing Protocol (EIGRP), click the following link to view an introduction to Enhanced Interior Gateway Routing Protocol (EIGRP).

Enhanced Interior Gateway Routing Protocol (EIGRP) Configuration

Enhanced Interior Gateway Routing Protocol (EIGRP) can be configured in a router using the following IOS commands.

Router(config)# router eigrp ASN
Router(config-router)# network Network_ID

ASN in the above IOS command stands for Autonomous System Number.

Enhanced Interior Gateway Routing Protocol (EIGRP) - Lab Practice

The following diagram shows our lab setup. We have three routers, three switches and three hosts connected as below. The host names, IP addresses and the interfaces of the routers are shown in diagram. The IP addresses of the hosts are also shown in the diagram.

If you are not familiar with a router console connection, click the following link to learn how to connect the serial port of your computer to router console port.
Click the following link to learn how to connect to the console port of the router if there is no serial port in your computer.
Click the following links to learn how to use HyperTerminal terminal emulator and PuTTY terminal emulator to configure router.

Hostname and IP address configuration in Router01

Connect to Router01 console and use the following IOS commands to configure host name as Router01.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router01
Router01(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router01 and configure IP address as 172.16.0.1/16.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface fa0/0
Router01(config-if)#ip address 172.16.0.1 255.255.0.0
Router01(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router01 and configure IP address as 172.17.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/0 interface, since this is the DCE side.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface s0/0
Router01(config-if)#clock rate 64000
Router01(config-if)#ip address 172.17.0.1 255.255.0.0
Router01(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router02

Connect to Router02 console and use the following IOS commands to configure host name as Router02.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router02
Router02(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router02 and configure IP address as 172.18.0.1/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface fa0/0
Router02(config-if)#ip address 172.18.0.1 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router02 and configure IP address as 172.17.0.2/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/0
Router02(config-if)#ip address 172.17.0.2 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router02 and configure IP address as 172.19.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/1 interface, since this is the DCE side.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#interface s0/1
Router02(config-if)#clock rate 64000
Router02(config-if)#ip address 172.19.0.1 255.255.0.0
Router02(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router03

Connect to Router03 console and use the following IOS commands to configure host name as Router03.

Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Router03
Router03(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router03 and configure IP address as 172.20.0.1/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface fa0/0
Router03(config-if)#ip address 172.20.0.1 255.255.0.0
Router03(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router03 and configure IP address as 172.19.0.2/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#interface s0/1
Router03(config-if)#ip address 172.19.0.2 255.255.0.0
Router03(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Enhanced Interior Gateway Routing Protocol (EIGRP) configuration in Router01

Connect to Router01 console and use the following IOS commands to configure Enhanced Interior Gateway Routing Protocol (EIGRP) in Router01. Please refer the beginning of this lesson to view the Enhanced Interior Gateway Routing Protocol (EIGRP) configuration IOS command.
In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#router eigrp 1
Router01(config-router)#network 172.16.0.0
Router01(config-router)#network 172.17.0.0
Router01(config-router)#exit
Router01(config)#exit
Router01#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Enhanced Interior Gateway Routing Protocol (EIGRP) configuration in Router02

Connect to Router02 console and use the following IOS commands to configure Enhanced Interior Gateway Routing Protocol (EIGRP) in Router02. Please refer the beginning of this lesson to view the Enhanced Interior Gateway Routing Protocol (EIGRP) configuration IOS command.
In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)#router eigrp 1
Router02(config-router)#network 172.17.0.0
Router02(config-router)#network 172.18.0.0
Router02(config-router)#network 172.19.0.0
Router02(config-router)#exit
Router02(config)#exit
Router02#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Enhanced Interior Gateway Routing Protocol (EIGRP) configuration in Router03

Connect to Router03 console and use the following IOS commands to configure Enhanced Interior Gateway Routing Protocol (EIGRP) in Router03. Please refer the beginning of this lesson to view the Enhanced Interior Gateway Routing Protocol (EIGRP) configuration IOS command.
In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)#router eigrp 1
Router03(config-router)#network 172.19.0.0
Router03(config-router)#network 172.20.0.0
Router03(config-router)#exit
Router03(config)#exit
Router03#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

How to view the routing table in Router01

After the initial configuration and Enhanced Interior Gateway Routing Protocol (EIGRP) configuration in all routers, we can use the "show ip route" to view the routing table in Router01, as shown below.

Router01>enable
Router01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

C 172.16.0.0/16 is directly connected, FastEthernet0/0
C 172.17.0.0/16 is directly connected, Serial0/0
D 172.18.0.0/16 [90/2172416] via 172.17.0.2, 00:05:36, Serial0/0
D 172.19.0.0/16 [90/2681856] via 172.17.0.2, 00:05:30, Serial0/0
D 172.20.0.0/16 [90/2684416] via 172.17.0.2, 00:02:35, Serial0/0

The "D" character at the beginning of a line in routing table shows that it is a route discovered by Enhanced Interior Gateway Routing Protocol (EIGRP) and "C" character shows that it is a directly connected network.

How to view the routing table in Router02

After the initial configuration and Enhanced Interior Gateway Routing Protocol (EIGRP) configuration in all routers, we can use the "show ip route" to view the routing table in Router02, as shown below.

Router02>enable
Router02#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

D 172.16.0.0/16 [90/2172416] via 172.17.0.1, 00:08:02, Serial0/0
C 172.17.0.0/16 is directly connected, Serial0/0
C 172.18.0.0/16 is directly connected, FastEthernet0/0
C 172.19.0.0/16 is directly connected, Serial0/1
D 172.20.0.0/16 [90/2172416] via 172.19.0.2, 00:04:45, Serial0/1

The "D" character at the beginning of a line in routing table shows that it is a route discovered by Enhanced Interior Gateway Routing Protocol (EIGRP) and "C" character shows that it is a directly connected network.

How to view the routing table in Router03

After the initial configuration and Enhanced Interior Gateway Routing Protocol (EIGRP) configuration in all routers, we can use the "show ip route" to view the routing table in Router03, as shown below.

Router03>enable
Router03#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route

Gateway of last resort is not set

D 172.16.0.0/16 [90/2684416] via 172.19.0.1, 00:06:01, Serial0/1
D 172.17.0.0/16 [90/2681856] via 172.19.0.1, 00:06:01, Serial0/1
D 172.18.0.0/16 [90/2172416] via 172.19.0.1, 00:06:01, Serial0/1
C 172.19.0.0/16 is directly connected, Serial0/1
C 172.20.0.0/16 is directly connected, FastEthernet0/0

The "D" character at the beginning of a line in routing table shows that it is a route discovered by Enhanced Interior Gateway Routing Protocol (EIGRP) and "C" character shows that it is a directly connected network.

Verify the connectivity between networks using the ping command

To verify the Enhanced Interior Gateway Routing Protocol (EIGRP) routes and the connectivity between networks, run the ping command from Host01 (IP address: 172.16.0.10/16) to Host03 (IP address: 172.20.0.10/16).

C:\>ping 172.20.0.10

Pinging 172.20.0.10 with 32 bytes of data:

Reply from 172.20.0.10: bytes=32 time=172ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125
Reply from 172.20.0.10: bytes=32 time=157ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125

Ping statistics for 172.20.0.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 157ms, Maximum = 188ms, Average = 176ms

The ping reply from Host03 (IP address: 172.20.0.10/16) shows that the Enhanced Interior Gateway Routing Protocol (EIGRP) Protocol is configured well in three routers and there is network connectivity between different networks.