Enhanced IGRP (EIGRP)
1. EIGRP Basics
1.1 Enhanced IGRP (EIGRP) is a balanced hybrid routing protocol. It has some features
similar to distance vector routing protocols and some features similar to link-state
routing protocols. It has the following characteristics:
Routing Protocol Type
Ÿ Cisco-proprietary protocol.
Ÿ Internal routing protocol.
Ÿ Classless routing protocol, i.e. support VLSM.
Ÿ EIGRP implements protocol-dependent modules for IP, IPX and AppleTalk. They
support routing for the specific Layer 3 protocols.
Metric
Ÿ Composite metric is used, which is computed using the IGRP metric formula (details
can be found in Chapter 3), and is then multiplied by 256 to achieve a finer metric
granularity, i.e. Default Metric = (Bw + Delay) x 256, where:
Ÿ Bw = [10 Gbps / bandwidth of the slowest link along the path].
Ÿ Delay = Sum of delays of all the links along the path (in 10s of microseconds).
Ÿ The maximum allowable hop count is 255 (100 by default).
Ÿ Diffusing Update Algorithm (DUAL) is used to calculate the shortest paths and
alternative routes. It exchanges more topology information than distance vector
routing protocols, but less than link-state routing protocols.
Ÿ Load-balancing using equal or unequal cost paths is supported.
Convergence
Ÿ Short convergence time (several seconds). EIGRP maintains backup routes (known
as feasible successors) in its topology database. When a route fails, EIGRP can use
its feasible successor immediately. Therefore, the convergence time can be very
short.
Neighbor Relationship
Ÿ A neighbor is a directly connected router running EIGRP and with the same AS
number.
Ÿ A router sends hello messages to its neighbors periodically when the hello timer
expires. The messages are used for neighbor discovery and maintenance.
CCNP BSCI 642-801 Exam Notes - Enhanced IGRP 2
Ÿ A neighbor is assumed dead if no hello message from that neighbor is received
before the hold timer expires (default = 3 times of the hello timer value). All
routes learned from that neighbor will also be deleted.
Routing updates
Ÿ Reliable Transport Protocol (RTP), a Cisco proprietary protocol, is used for
transmitting EIGRP messages between routers. It can provide reliable packet
delivery when necessary, by using sequence number, acknowledgement, and
retransmission with unicast (a packet will be retransmitted up to 16 times if no
acknowledgement is received, before declaring the neighbor router is dead).
Ÿ Both unicast and multicast traffic are used for inter-router communication. The
multicast address used by EIGRP is 224.0.0.10.
Ÿ Partial routing updates are sent between neighbors when there are link-state changes.
Full routing updates (the entire topology table) are not sent regularly. They are sent
only when two neighbors initiate communication.
Ÿ Authentication of the source of routing updates is supported.
1.2 EIGRP consists of four components :
Ÿ Protocol-dependent modules
Ÿ Diffusing Update Algorithm (DUAL)
Ÿ Neighbor discovery/recovery
Ÿ Reliable Transport Protocol (RTP)
1.3 EIGRP classifies the next hop routers of different paths from the router to a destination
network as follows:
Ÿ Successor
Ÿ The next hop router of the lowest cost path to the destination network.
Ÿ It is placed in the routing table.
Ÿ Feasible distance (FD) refers to the metric of the lowest cost path from the
router to the destination network.
Ÿ Feasible successors (FS)
Ÿ The next hop routers of the paths that meet the feasible condition.
Ÿ Feasible condition (FC) refers to the condition that the metric of the path from
the next hop router to the destination network is lower than the router's feasible
distance. It implies that the next hop router is downstream from the router, and
the path from the next hop router to the destination network does not pass
through the router. Therefore, routing loops can be prevented with the FC
checking.
Ÿ Possibilities
Ÿ The next hop routers of the paths that cannot meet the feasible condition.
1.4 EIGRP classifies routes into the following three types:
Ÿ Internal routes
Ÿ Routes that are learned within this EIGRP AS.
Ÿ The default administrative distance of EIGRP internal routes is 90.
Ÿ In the output of the command "#show ip route", EIGRP internal routes are
represented by the code "D". For example:
D 192.168.1.0/24 [90/2674123] via 10.1.1.6, 0:01:00, Ethernet0
Ÿ External routes
Ÿ Routes that are redistributed into this EIGRP AS from another routing process.
Ÿ IP EIGRP automatically redistributes routes with IP IGRP of the same AS.
Ÿ IPX EIGRP automatically redistributes routes with IPX RIP and NLSP.
Ÿ AppleTalk EIGRP automatically redistributes routes with AppleTalk RTMP.
Ÿ The default administrative distance of EIGRP external routes is 170.
Ÿ In the output of the command "#show ip route", EIGRP external routes are
represented by the code "D EX". For example:
D EX 172.31.1.0/24 [170/3110962] via 10.1.3.5, 0:01:31, Ethernet1
Ÿ Summary routes
Ÿ Summary routes advertised by a router performing summarization on morespecific
EIGRP routes.
Ÿ EIGRP can perform route summarization at any interface on any router (rather
than on an area border router only for OSPF).
Ÿ Auto-summarization (i.e. automatic route summarization at classful network
boundary) is enabled by default. To manually configure summarization, autosummarization
should be disabled first.
Ÿ A router performing route summarization will automatically create a static route
to the null interface (null0) for the summarized address. This ensures that if the
router receives a packet destined for an address within the summarized address
range, and for which it has no route (e.g. 172.31.111.0 in the example below), it
will forward the packet to the null interface (i.e. drop the packet), rather than
using some other routes such as the default route for routing the packet.
Ÿ An example of the output of the command "#show ip route" on a router
performing route summarization is as follows:
172.31.0.0/16 is subnetted, 2 subnets
C 172.31.100.0/24 is directly connected, Ethernet0
C 172.31.101.0/24 is directly connected, Ethernet1
D 172.31.0.0/16 is a summary, 0:01:19, Null0
Ÿ The metric of a summary route is the best metric among the summarized routes.
Ÿ The default administrative distance of EIGRP summary routes is 5.
CCNP BSCI 642-801 Exam Notes - Enhanced IGRP 4
Ÿ In the output of the command "#show ip route" on a router received an EIGRP
summary route, the route is represented by the code "D", same as an EIGRP
internal route.
2. EIGRP Operation
2.1 EIGRP makes use of the following three tables in its operation:
Ÿ Neighbor table.
Ÿ Topology table.
Ÿ Routing table.
Each Layer 3 protocol supported by EIGRP (i.e. IP, IPX, and AppleTalk) has its own set
of tables. Therefore, there are 9 active EIGRP tables on a router if EIGRP is configured
for all the three Layer 3 protocols.
2.2 Neighbor table has the following characteristics:
Ÿ A neighbor table contains an entry for each neighbor.
Ÿ Each entry in the table (IP) contains the following information of a neighbor:
Ÿ IP address of the neighbor.
Ÿ Interface of the router connected to the neighbor.
Ÿ The neighbor's uptime, or how long the neighbor was added to the neighbor table.
Ÿ Hold-time - how long the router waits before considering the neighbor is down.
Ÿ Smooth round-trip time (SRTT) - the time period for a packet to be sent to the
neighbor and a reply to be received. It is used to calculate the RTO.
Ÿ Retransmission timeout (RTO) - the time period that the router will wait for an
acknowledgement from the neighbor before re-transmitting a packet.
Ÿ The sequence number of the last EIGRP packet received from the neighbor.
Ÿ Number of EIGRP packets that the router is waiting to send to the neighbor.
Ÿ etc.
2.3 Topology table has the following characteristics:
Ÿ It contains an entry for every destination network learned through EIGRP.
Ÿ Each table entry contains the following information of a destination:
Ÿ IP address prefix and netmask of the destination network.
Ÿ Feasible distance.
Ÿ Successors.
Ÿ For each path to the destination network:
Ÿ IP address of the next hop router (i.e. either a successor, feasible successor, or
possibility).
5 CCNP BSCI 642-801 Exam Notes - Enhanced IGRP
Ÿ Advertised Distance (AD), also known as Reported Distance (RD), i.e. the
metric of the path from the next hop router to the destination network (metric
advertised by the next hop router).
Ÿ Outgoing interface connected to the next hop router.
Ÿ Status of the route to the destination network - Passive (i.e. healthy) or Active
(i.e. the router is querying its neighbors to find a path to the network).
Ÿ Whether the router has sent an update / query / reply packet about the route to its
neighbors, or is waiting for a reply.
2.4 Routing table has the following characteristics:
Ÿ It is built from the topology table after DUAL has been run.
Ÿ The table contains the following information for each destination:
Ÿ IP address prefix and netmask of the destination network.
Ÿ Successors for the destination network. Up to six successors (four by default)
can be placed in the routing table for each destination network. This number is
configurable.
2.5 There are five type of EIGRP packets:
Ÿ Hello packet
Ÿ It is used for discovering neighbors and maintaining neighbor relationship.
Ÿ It is sent to neighbors periodically (hello interval). The default hello interval is:
Ÿ Non-broadcast multi-access (NBMA) network with bandwidth <= 1.5 Mbps
(e.g. T1 frame relay, ISDN BRI, etc.) - 60 seconds .
Ÿ Other networks (e.g. Ethernet, point-to-point serial links, high speed frame
relay, etc.) - 5 seconds .
Ÿ A neighbor is assumed dead if no hello message from that neighbor is received
before the hold timer expires (default = 3 times of the hello timer value). All
routes learned from that neighbor will also be deleted.
Ÿ Neighbor routers can use different hello and hold-time intervals. A router
informs the neighbors its hold-time interval through hello packets.
Ÿ It is sent as multicast.
Ÿ Acknowledgement is not required (i.e. unreliable delivery).
Ÿ Update packet
Ÿ It is used for sending routing information to neighbors as follows:
Ÿ Full routing updates (i.e. the whole topology table) during initialization of
the routing process.
Ÿ Incremental routing updates (i.e. routing updates about the paths that have
been changed) when there is a change in the network topology or metric.
Ÿ It is sent to the relevant routers as unicast or multicast.
Ÿ Acknowledgement is required (i.e. reliable delivery).
Ÿ Query packet
Ÿ It is used for querying neighbors if they have feasible successors for a destination
network.
Ÿ It is sent during a diffusing computation (to be explained later in this Section).
Ÿ It is sent as multicast.
Ÿ Acknowledgement is required (i.e. reliable delivery).
Ÿ Reply packet
Ÿ It is used for replying a query with the requested routing information (e.g.
information of the best path to the destination network, or destination
unreachable).
Ÿ It is sent as unicast.
Ÿ Acknowledgement is required (i.e. reliable delivery).
Ÿ Acknowledgement (ACK) packet
Ÿ It is used for acknowledging the receipt of an update / query / reply packet.
Ÿ It is sent as unicast.
Ÿ Acknowledgement is not required (i.e. unreliable delivery).
2.6 Diffusing Update Algorithm (DUAL) is used to determine the successors and feasible
successors for a destination network. A router will run DUAL when:
Ÿ There is a change in the status or metric of a directly connected link.
Ÿ An update is received from a neighbor (through update / query / reply packet).
2.7 DUAL works as follows:
1. Local Computation
Ÿ The router recalculates the distance to the destination network for each feasible
successor.
Ÿ If the lowest distance is smaller than the FD:
Ÿ The corresponding feasible successor will become the new successor.
Ÿ The FD will be revised to the lowest distance value.
Ÿ Routing updates will be sent to the neighbors.
Ÿ When the router is performing a local computation, the route remains in the
passive state.
Ÿ If a feasible successor for the route cannot be found in the topology table, the
router will run the diffusing algorithm.
2. Diffusing Computation
Ÿ The state of the route is changed from passive to active.
Ÿ The router sends queries to its neighbors to ask for routes to the destination
network.
Ÿ When a neighbor receives the query, it will perform a local computation. If one
or more feasible successors are found, the neighbor will send a reply back to the
querying router with the best route. Otherwise, it will perform a diffusing
computation. Therefore, the query will propagate or diffuse until a reply is
received. If no feasible successor can be found eventually, the neighbor returns
an unreachable message to the querying router.
Ÿ The router waits for a reply from every neighbor it queried until the active timer
(default = 3 minutes) expires. The active timer is designed to prevent a route
from being permanently active.
Ÿ The router updates its topology table with the replies received. The metric for
each feasible successor is calculated based on the cost advertised by the neighbor
and the cost of the link to the neighbor.
Ÿ The feasible successor with the lowest metric is selected as the successor, and the
feasible distance is updated accordingly.
Ÿ The state of the route is changed from active to passive.
3. Scalability & Performance
3.1 A route will be marked as stuck-in-active (SIA) if one or more neighbors do not reply to
a query for the route before the active timer expires. The unresponsive neighbors will
be removed from the neighbor table. The routes with these neighbors as the next hop
router will also be deleted.
3.2 SIAs should not occur in a stable and well-designed network. If a neighbor router or a
link has problem, it should be detected by the expiry of the hold timer, long before the
expiry of the active timer. Therefore, such problems will not cause SIAs normally.
3.3 However, SIAs may occur because of looping of queries, or because of heavily
congested / low-bandwidth links and/or overloaded routers in a large network.
Therefore, SIAs may lead to flushing of valid neighbors and routes from the neighbor
table and topology table, which affect the stability of the network.
3.4 Route queries can propagate throughout the entire network if feasible successors are not
found. It causes scalability limitation on the network size and may even lead to SIAs.
The problem is more complicated if the network contains redundant paths, such that the
queries may loop back. To prevent these problems, the following methods can be used
to limit the scope of query range, i.e. query scoping:
Ÿ Route summarization. If a subnet is hidden in route summarization, the router
will reply that the subnet is unreachable and the querying router will purge the route
from its database. It is the most effective method for limiting the scope of query
range.
Ÿ EIGRP Stub Feature. In a hub-and-spoke network, by configuring the remote
routers as stubs, the hub router can answer queries immediately without propagating
the queries to the remote sites.
Ÿ Autonomous System Boundary. Queries do not propagate into other ASs unless
redistribution with the ASs has been configured.
Ÿ Route Filtering. Filters for routing updates (details can be found in Chapter 7) can
be used to mark query replies as unreachable.
3.5 The EIGRP Stub Routing feature can improve network stability (by preventing SIAs)
and reduce resources required on stub routers. It has the following characteristics:
Ÿ It is typically used in a hub-and-spoke network (similar to ODR).
Ÿ It is suitable for stub routers (stub networks' routers which connected to the
distribution router or the hub) with limited resources.
Ÿ Since the stub routers have no EIGRP neighbor router other than the distribution
router (hub), they must forward all non-local traffic to the distribution router.
Therefore, the routers do not need to maintain full topology tables and routing tables,
but only a default route to the distribution router for non-local traffic.
Ÿ With the stub routing feature enabled, the stub routers direct all non-local traffic to
the distribution router. Besides, the distribution router will not query the stub
routers for any routes (i.e. query scoping).
3.6 EIGRP controls the bandwidth usage of a link for transmitting EIGRP traffic. This
feature is known as pacing. It works as follows:
Ÿ By default, at most 50% of the configured bandwidth of an interface or subinterface
is used for transmitting EIGRP traffic. It prevents the routing traffic from saturating
the link. Otherwise, data packets and EIGRP packets may be dropped.
Ÿ For a LAN interface, the default bandwidth value reflects the correct bandwidth.
No additional manual configuration is required normally.
Ÿ For a serial interface, the default bandwidth value is always 1544 or 1.544 Mbps.
Therefore, the bandwidth value may need to be configured manually using the
command "(config-if)#bandwidth".
Ÿ For a point-to-point subinterface, the default bandwidth value is also 1.544 Mbps.
Therefore the following manual configuration is required:
Ÿ Configure the bandwidth value as the committed information rate (CIR) of the
subinterface (e.g. frame relay DLCI).
Ÿ If the total bandwidth (for all subinterfaces of the physical interface) that can be
9 CCNP BSCI 642-801 Exam Notes - Enhanced IGRP
used by EIGRP traffic exceeds the access speed of the physical interface, reduce
the percentage of the configured bandwidth that can be used by EIGRP traffic
using the command "(config-if)#ip bandwidth-percent eigrp".
Ÿ For a multi-point subinterface, the bandwidth value for each virtual circuit (VC) is
the subinterface bandwidth / number of virtual circuits. If the VCs have different
CIR values, the VCs with lower CIR may be saturated by EIGRP traffic. To solve
this problem, the following approaches can be used:
Ÿ Manually configure the bandwidth value of the subinterface as the minimum
CIR x number of virtual circuits (this approach may cause inefficient usage of
the bandwidth for VCs with higher CIR); or
Ÿ Use point-to-point configuration instead of multi-point configuration, so that a
different bandwidth value can be configured for each subinterface. This
approach is the recommended solution.
Ÿ The bandwidth allocated to EIGRP traffic for a VC should be the same on both ends
of the circuit.
3.7 EIGRP does not require any special configuration for it to work on different types of
Layer 2 networks, other than the bandwidth usage control mentioned above. Other
routing protocols, such as OSPF, require different configurations for different types of
Layer 2 networks (e.g. Ethernet and Frame Relay).
4. Configuring EIGRP
4.1 The following commands are used for basic EIGRP configuration:
Command Description
(config)#[no] router eigrp
<AS number>
Ÿ Turn on the EIGRP routing process and enter
the router configuration mode "(configrouter)#"
(or turn off the EIGRP routing
process).
Ÿ All routers must use the same AS number in
order to share their routing information. The
AS number can be assigned arbitrarily within
the range 1 - 65535.
Ÿ No EIGRP routing process is defined by
default.
(config-router)#[no] network
<ip address> [<mask>]
Ÿ Add (or remove) the specified directly
connected network to the EIGRP AS.
Ÿ The router will then establish neighbor
relationship with other EIGRP routers through
the local interfaces that are configured with
addresses under the specified network.
Ÿ Optionally, a netmask or wildcard mask can be
used for specifying the interfaces to be added
to the routing process. If it is not specified,
classful network address is used.
Ÿ There is no limit to the number of "(configrouter)#
network" commands that can be issued
on the router.
(config-router)#[no]
passive-interface
<int-type> <int-num>
(config-router)#passive-interface
default
Ÿ Disable (or re-enable) sending of hello
messages out the specified interface.
Therefore, neighbor relationship cannot be
established, and no routing traffic will be sent
or received.
Ÿ An interface is non-passive by default.
Ÿ The keyword “default” sets all interfaces as
passive by default.
4.2 An example of configuring EIGRP is as follows:
Router(config)#interface ethernet 1
Router(config-if)#ip address 192.168.1.1
255.255.255.0
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#interface ethernet 2
Router(config-if)#ip address 192.168.2.1
255.255.255.0
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#router eigrp 1
Router(config-router)#network 192.168.0.0
0.0.255.255
Router(config-router)#exit
Ÿ Define the IP address of the interface
and the network directly connected.
Ÿ Define the IP address of another
interface and the network directly
connected.
Ÿ Enable EIGRP routing for the two
interfaces.
4.3 The following commands are used for configuring load-balancing :
Command Description
(config-router)#maximum-paths
<number of paths>
(config-router)#no maximum-paths
Ÿ Set the maximum number (valid values are 1-
6) of equal or unequal-cost routes for a
destination network that will be kept in the
routing table (or reset to the default value).
Ÿ The default value is 4.
(config-router)#variance
<multiplier>
(config-router)#no variance
Ÿ Set the variance multiplier (or reset to the
default value).
Ÿ Any route with the metric lower than or equal
to the lowest metric x variance will be added
into the routing table.
Ÿ If the "maximum-paths" has been reached,
only the lowest metric routes are kept in the
routing table.
Ÿ The default variance multiplier is 1, i.e. only
the routes with the path cost equals the lowest
metric will be put in the routing table.
(config-router)#[no] traffic-share min
[across-interfaces]
Ÿ Configure the router to use the route with the
lowest metric when there are multiple routes
to the same destination network in the routing
table.
Ÿ It means that the load-balancing function
using unequal-cost routes is turned off.
However, if the route with the lowest metric
fails, the route with the next lowest metric can
still be used immediately without waiting for
convergence of the network.
Ÿ The keyword "across-interfaces" allows you to
configure multi-interface load splitting on
different interfaces with equal cost paths.
Ÿ The "no" form of the command disables this
function.
(config-router)#[no] traffic-share
balanced
Ÿ Configure the router to distribute traffic
among all the routes for the same destination
network in the routing table.
Ÿ Routes with higher metrics are less-preferable
and get less traffic.
Ÿ The "no" form of the command disables this
function.
Ÿ This function is enabled by default.
However, since the default variance multiplier
is 1, the default behavior is load-balancing
over equal-cost paths.
4.4 An example of configuring load-balancing is as follows:
Router(config)#router eigrp 1
Router(config-router)#network 192.168.0.0
0.0.255.255
Router(config-router)#maximum-paths 6
Router(config-router)#variance 2
Ÿ Set the maximum number of routes per
destination as 6.
Ÿ For each destination, install rout
Router(config-router)#traffic-share
balanced
Router(config-router)#exit
with metrics <= the lowest metric x 2.
Ÿ Enable load-balancing over unequalcost
routes. This function is enabled
by default. Therefore, this command
is actually not necessary.
4.5 The following commands are used for configuring route summarization:
Command Description
(config-router)#[no] auto-summary Ÿ Enable (or disable) auto-summarization.
Ÿ Prior to IOS version 12.2, auto-summarization
is enabled by default for EIGRP. On newer
versions IOS, it is disabled by default.
(config-if)#[no] ip summary-address
eigrp <AS number>
<network-address> <netmask>
[<admin-distance>]
Ÿ Configure EIGRP to summarize the routes for
the subnets covered by the specified network
address and netmask, and advertise the
summary route out the interface (or disable the
configuration).
Ÿ A route to the null interface (null0) for the
summarized address will also be created.
Ÿ Optionally, the administrative distance of the
summary route can be specified.
(config-if)#no ip unreachables Ÿ Disable the generation of ICMP unreachable
messages.
Ÿ By default, the router generates an ICMP
unreachable message to the source of a packet
dropped by the null interface. With this
command, the packet will be dropped silently.
4.6 An example of configuring route summarization is as follows:
Router(config)#interface ethernet 0
Router(config-if)#ip address 172.16.1.1
255.255.255.0
Router(config-if)#exit
Router(config)#interface ethernet 1
Router(config-if)#ip address 172.16.2.1
255.255.255.0
Router(config)#router eigrp 1
Router(config-router)#no auto-summary
Router(config-router)#network 172.16.1.0
Router(config-router)#network 172.16.2.0
Ÿ Configure interface Ethernet 0.
Ÿ Configure interface Ethernet 1.
Ÿ Disable auto-summarization.
Ÿ Enable EIGRP routing for the two
interfaces.
Router(config-router)#exit
Router(config)#interface serial 0
Router(config-if)#ip address 10.5.12.1
255.255.255.0
Router(config-if)#ip summary-address
eigrp 1 172.16.0.0 255.255.0.0
Router(config-if)#exit
Ÿ Configure interface Serial 0.
Ÿ Advertise a summary route for
172.16.0.0/16, instead of the two more
specific routes 172.16.1.0/24 and
172.16.2.0/24, out the interface Serial
0.
4.7 The following commands are used for tuning EIGRP parameters and configuring
EIGRP stub routing:
Command Description
(config-if)#[no] ip hello-interval
eigrp <AS-number>
<hello interval in seconds>
Ÿ Configure the hello interval for the specified
EIGRP AS on the interface (or reset to the
default value).
Ÿ The smaller the hello interval (and the holdtime
interval), the faster the network
converges. However, more routing traffic
will be generated.
Ÿ The default hello interval is 60 seconds for
NBMA networks with bandwidth <= 1.5
Mbps, and 5 seconds for other networks.
(config-if)#[no] ip hold-time
eigrp <AS number>
<hold-time interval in seconds>
Ÿ Configure the hold-time interval for the
specified EIGRP AS on the interface (or reset
to the default value).
Ÿ The hold-time interval should at least equal
three times the hello interval.
Ÿ The default hold-time interval is 180 seconds
for NBMA networks with bandwidth <= 1.5
Mbps, and 15 seconds for other networks.
(config-if)#[no] ip
bandwidth-percent eigrp
<AS number> <percent>
Ÿ Configure the maximum percentage of
bandwidth that may be used by the specified
EIGRP AS on the interface (or reset to the
default value).
Ÿ The default value is 50%.
(config-router)#[no] eigrp stub
[receive-only | connected |
static | summary]
Ÿ Configure the router as an EIGRP stub router
(or disable the configuration).
Ÿ The keyword "receive-only" restricts the
router from advertising any of its routes.
This keyword cannot be used together with
any other keyword.
Ÿ The keyword "connected" permits the router to
advertise connected routes. It is enabled by
default.
Ÿ The keyword "static" permits the router to
advertise redistributed static routes. It is
disabled by default.
Ÿ The keyword "summary" permits the router to
advertise summary routes. It is enabled by
default.
Ÿ The keywords "connected", "static", and
"summary" can be used in any combination.
If the command is issued with any of these
three keywords, the router will be permitted to
advertise the corresponding types of routes,
but restricted from advertising the types of
routes not specified.
Ÿ No special configuration is required on the
distribution router.
4.8 The following commands are used for debugging EIGRP information:
Command Description
#[no] debug eigrp packet Ÿ Enable (or disable) debugging of transmission
and receipt of EIGRP packets.
#[no] debug eigrp neighbor Ÿ Enable (or disable) debugging of EIGRP
neighbor information.
#[no] debug ip eigrp Ÿ Enable (or disable) debugging of EIGRP
routing updates (including routes and metrics
information).
#[no] debug ip eigrp notifications Ÿ Enable (or disable) debugging of EIGRP
events and notifications.
4.9 The following commands are used for showing EIGRP information:
Command Description
#show ip route eigrp Ÿ Show routing table entries learned through
EIGRP.
#show ip route
<destination network address>
[<subnet mask>]
Ÿ Show detail information of the specified route
including:
Ÿ Destination network address and netmask.
Ÿ Routing protocol (i.e. EIGRP) and AS
number from which this route is learned.
Ÿ Administrative distance.
Ÿ Route metric.
Ÿ Redistribution protocol.
Ÿ The last time the route was updated (in
hh:mm:ss), the source of the update, and the
interface received the update.
Ÿ Next hop IP address.
Ÿ Delay (in microseconds), bandwidth (in
kbps), reliability (1-255), load (1-255),
MTU (in bytes) of the route.
Ÿ etc.
#show ip protocols Ÿ Show the parameters and current state of each
active routing protocol process.
Ÿ For EIGRP, the following information are
shown:
Ÿ AS number.
Ÿ Whether the incoming and outgoing
filtering list ha ve been set.
Ÿ The protocol(s) that is being redistributed.
Ÿ Whether automatic route summarization has
been enabled.
Ÿ The networks for which the routing process
is currently injecting routes.
Ÿ Routing Information Sources. For each
source, the following information are
shown:
Ÿ IP address of the source/neighbor.
Ÿ Administrative distance.
Ÿ Time of the last update received from the
source.
Ÿ etc.
#show ip eigrp interfaces
[<int-type> <int-num>]
[<AS number>]
Ÿ Show EIGRP-related interface information for
all EIGRP interfaces, or the specified
interface, or the interfaces configured with the
specified AS.
Ÿ The following information are shown for each
interface:
Ÿ Interface name.
Ÿ Number of directly connected neighbors
(peers), etc.
#show ip eigrp neighbors
[<AS number>] [detail]
Ÿ Show EIGRP neighbor information.
Ÿ The following information are shown for each
neighbor:
Ÿ IP address of the neighbor.
Ÿ Interface that is connected to the neighbor.
Ÿ AS number.
Ÿ Hold-time, i.e. length of time that the router
will wait to hear from the neighbor before
declaring it is down.
Ÿ Uptime, i.e. elapsed time (in hours:minutes:
seconds) since the router first heard from
this neighbor.
Ÿ Number of EIGRP packets (update, query,
and reply) that the router is waiting to send.
Ÿ Sequence number of the last update, query,
or reply packet that was received from this
neighbor.
Ÿ Smooth round-trip time (SRTT) (in ms)
required for an EIGRP packet to be sent to
the neighbor and an acknowledgment of
that packet to be received.
Ÿ Retransmission time-out (RTO) (in ms).
Ÿ If the keyword "detail" is specified, the
following additional information will also be
shown for each neighbor:
Ÿ The IOS version of the neighbor.
Ÿ The number of times that a packet has been
retransmitted.
Ÿ The number of times an attempt was made to
retransmit a packet.
Ÿ Elapsed time (in hours:minutes:seconds)
since the neighbor has restarted.
#show ip eigrp topology
[<AS number> |
{<ip-address> [<netmask>]}]
[summary]
Ÿ Show all entries in the EIGRP topology
database, or only the entries of the specified
AS or destination IP address.
Ÿ The following information are shown for each
entry (destination network):
Ÿ Entry state (passive, active, update, query,
or reply). In a stable network, all entries
should be in the passive state. Active state
indicates that the router has lost its path to
the destination and is searching for a
replacement. Update/query/reply state
indicates that an update/query/reply packet
was sent.
Ÿ Destination network address and netmask.
Ÿ Feasible distance, i.e. the best metric to
reach the destination.
Ÿ Number of successors, i.e. the number of
next hops that are selected into the routing
table.
Ÿ For each known next hop to the destination,
the following information are shown:
Ÿ IP address of the peer which advertises
the path (i.e. the next hop router).
Ÿ The interface from which the path is
learned (i.e. the outgoing interface).
Ÿ The EIGRP metric that represents the
cost from the router to the destination.
Ÿ The EIGRP metric that the peer
advertises (i.e. the cost from the peer to
the destination). It is known as the
advertised distance.
#show ip eigrp traffic
[<AS number>]
Ÿ Show the number of EIGRP packets (hello,
update, query, reply, or ack) sent and received
for each AS, or the specified AS.
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