Configuring EIGRP

This chapter describes how to configure the Enhanced Interior Gateway Routing Protocol ( EIGRP) on Cisco NX-OS switches.

This chapter includes the following sections:

Information About EIGRP

EIGRP combines the benefits of distance vector protocols with the features of link-state protocols. EIGRP sends out periodic hello messages for neighbor discovery. Once EIGRP learns a new neighbor, it sends a one-time update of all the local EIGRP routes and route metrics. The receiving EIGRP router calculates the route distance based on the received metrics and the locally assigned cost of the link to that neighbor. After this initial full route table update, EIGRP sends incremental updates to only those neighbors affected by the route change. This process speeds convergence and minimizes bandwidth.

EIGRP Components

EIGRP has the following basic components:

Reliable Transport Protocol

The Reliable Transport Protocol guarantees ordered delivery of EIGRP packets to all neighbors. (See the Neighbor Discovery and Recovery section.) The Reliable Transport Protocol supports the transmission of unicast packets. This provision helps to ensure that the convergence time remains low for various speed links. See the Configuring Advanced EIGRP section for details about modifying the default timers that control the unicast packet transmissions.

The Reliable Transport Protocol includes the following message types:

  • Hello—Used for neighbor discovery and recovery. By default, EIGRP sends a periodic multicast hello message on the local network at the configured hello interval. By default, the hello interval is 5 seconds.

  • Acknowledgement—Verifies reliable reception of Updates, Queries, and Replies.

  • Updates—Sends to affected neighbors when routing information changes. Updates include the route destination, address mask, and route metrics such as delay and bandwidth. The update information is stored in the EIGRP topology table.

  • Queries and Replies—Sent as necessary as part of the Diffusing Update Algorithm used by EIGRP.

Neighbor Discovery and Recovery

EIGRP uses the hello messages from the Reliable Transport Protocol to discover neighboring EIGRP routers on directly attached networks. EIGRP adds neighbors to the neighbor table. The information in the neighbor table includes the neighbor address, the interface it was learned on, and the hold time, which indicates how long EIGRP should wait before declaring a neighbor unreachable. By default, the hold time is three times the hello interval or 15 seconds.

EIGRP sends a series of Update messages to new neighbors to share the local EIGRP routing information. This route information is stored in the EIGRP topology table. After this initial transmission of the full EIGRP route information, EIGRP sends Update messages only when a routing change occurs. These Update messages contain only the new or changed information and are sent only to the neighbors affected by the change. See the EIGRP Route Updates section.

EIGRP also uses the hello messages as a keepalive to its neighbors. As long as hello messages are received, Cisco NX-OS can determine that a neighbor is alive and functioning.

Diffusing Update Algorithm

The Diffusing Update Algorithm (DUAL) calculates the routing information based on the destination networks in the topology table. The topology table includes the following information:

  • IPv4 address/mask—The network address and network mask for this destination.

  • Successors—The IP address and local interface connection for all feasible successors or neighbors that advertise a shorter distance to the destination than the current feasible distance.

  • Feasibility distance (FD)—The lowest calculated distance to the destination. The feasibility distance is the sum of the advertised distance from a neighbor plus the cost of the link to that neighbor.

DUAL uses the distance metric to select efficient, loop-free paths. DUAL selects routes to insert into the unicast Routing Information Base (RIB) based on feasible successors. When a topology change occurs, DUAL looks for feasible successors in the topology table. If there are feasible successors, DUAL selects the feasible successor with the lowest feasible distance and inserts that into the unicast RIB, avoiding unnecessary recomputation.

When there are no feasible successors but there are neighbors advertising the destination, DUAL transitions from the passive state to the active state and triggers a recomputation to determine a new successor or next-hop router to the destination. The amount of time required to recompute the route affects the convergence time. EIGRP sends Query messages to all neighbors, searching for feasible successors. Neighbors that have a feasible successor send a Reply message with that information. Neighbors that do not have feasible successors trigger a DUAL recomputation.

EIGRP Route Updates

When a topology change occurs, EIGRP sends an Update message with only the changed routing information to affected neighbors. This Update message includes the distance information to the new or updated network destination.

The distance information in EIGRP is represented as a composite of available route metrics, including bandwidth, delay, load utilization, and link reliability. Each metric has an associated weight that determines if the metric is included in the distance calculation. You can configure these metric weights. You can fine-tune link characteristics to achieve optimal paths, but we recommend that you use the default settings for most configurable metrics.

Internal Route Metrics

Internal routes are routes that occur between neighbors within the same EIGRP autonomous system. These routes have the following metrics:

  • Next hop—The IP address of the next-hop router.

  • Delay—The sum of the delays configured on the interfaces that make up the route to the destination network. Configured in tens of microseconds.

  • Bandwidth—The calculation from the lowest configured bandwidth on an interface that is part of the route to the destination.


Note

We recommend that you use the default bandwidth value. This bandwidth parameter is also used by EIGRP.

  • MTU—The smallest maximum transmission unit value along the route to the destination.

  • Hop count—The number of hops or routers that the route passes through to the destination. This metric is not directly used in the DUAL computation.

  • Reliability—An indication of the reliability of the links to the destination.

  • Load—An indication of how much traffic is on the links to the destination.

By default, EIGRP uses the bandwidth and delay metrics to calculate the distance to the destination. You can modify the metric weights to include the other metrics in the calculation.

External Route Metrics

External routes are routes that occur between neighbors in different EIGRP autonomous systems. These routes have the following metrics:

  • Next hop—The IP address of the next-hop router.

  • Router ID—The router ID of the router that redistributed this route into EIGRP.

  • AS Number—The autonomous system number of the destination.

  • Protocol ID—A code that represents the routing protocol that learned the destination route.

  • Tag—An arbitrary tag that can be used for route maps.

  • Metric—The route metric for this route from the external routing protocol.

EIGRP and the Unicast RIB

EIGRP adds all learned routes to the EIGRP topology table and the unicast RIB. When a topology change occurs, EIGRP uses these routes to search for a feasible successor. EIGRP also listens for notifications from the unicast RIB for changes in any routes redistributed to EIGRP from another routing protocol.

Advanced EIGRP

You can use the advanced features of EIGRP to optimize your EIGRP configuration.

Address Families

EIGRP supports the IPv4 address family.

Address family configuration mode includes the following EIGRP features:

  • Authentication

  • AS number

  • Default route

  • Metrics

  • Distance

  • Graceful restart

  • Logging

  • Load balancing

  • Redistribution

  • Router ID

  • Stub router

  • Timers

You cannot configure the same feature in more than one configuration mode. For example, if you configure the default metric in router configuration mode, you cannot configure the default metric in address family mode

Authentication

You can configure authentication on EIGRP messages to prevent unauthorized or invalid routing updates in your network. EIGRP authentication supports MD5 authentication digest.

You can configure the EIGRP authentication per virtual routing and forwarding (VRF) instance or interface using key-chain management for the authentication keys. Key-chain management allows you to control changes to the authentication keys used by MD5 authentication digest. See the Cisco Nexus 3548 Switch NX-OS Security Configuration Guide for more details about creating key-chains.

For MD5 authentication, you configure a password that is shared at the local router and all remote EIGRP neighbors. When an EIGRP message is created, Cisco NX-OS creates an MD5 one-way message digest based on the message itself and the encrypted password and sends this digest along with the EIGRP message. The receiving EIGRP neighbor validates the digest using the same encrypted password. If the message has not changed, the calculation is identical and the EIGRP message is considered valid.

MD5 authentication also includes a sequence number with each EIGRP message that is used to ensure that no message is replayed in the network.

Stub Routers

You can use the EIGRP stub routing feature to improve network stability, reduce resource usage, and simplify stub router configuration. Stub routers connect to the EIGRP network through a remote router. See the Stub Routing section.

When using EIGRP stub routing, you need to configure the distribution and remote routers to use EIGRP and configure only the remote router as a stub. EIGRP stub routing does not automatically enable summarization on the distribution router. In most cases, you need to configure summarization on the distribution routers.

Without EIGRP stub routing, even after the routes that are sent from the distribution router to the remote router have been filtered or summarized, a problem might occur. For example, if a route is lost somewhere in the corporate network, EIGRP could send a query to the distribution router. The distribution router could then send a query to the remote router even if routes are summarized. If a problem communicating over the WAN link between the distribution router and the remote router occurs, EIGRP could get stuck in active condition and cause instability elsewhere in the network. EIGRP stub routing allows you to prevent queries to the remote router.

Route Summarization

You can configure a summary aggregate address for a specified interface. Route summarization simplifies route tables by replacing a number of more-specific addresses with an address that represents all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with one summary address, 10.1.0.0/16.

If more specific routes are in the routing table, EIGRP advertises the summary address from the interface with a metric equal to the minimum metric of the more specific routes.


Note

EIGRP does not support automatic route summarization.

Route Redistribution

You can use EIGRP to redistribute direct routes, static routes, routes learned by other EIGRP autonomous systems, or routes from other protocols. You configure route map with the redistribution to control which routes are passed into EIGRP. A route map allows you to filter routes based on attributes such as the destination, origination protocol, route type, route tag, and so on. See Configuring Route Policy Manager.

You also configure the default metric that is used for all imported routes into EIGRP.

Load Balancing

You can use load balancing to allow a router to distribute traffic over all the router network ports that are the same distance from the destination address. Load balancing increases the utilization of network segments, which increases effective network bandwidth.

Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 32 equal-cost paths in the EIGRP route table and the unicast RIB. You can configure EIGRP to load balance traffic across some or all of those paths.


Note

EIGRP in Cisco NX-OS does not support unequal cost load balancing.

Note

In the Cisco Nexus 3548 switch, ECMP is not supported on warp mode.

Split Horizon

You can use split horizon to ensure that EIGRP never advertises a route out of the interface where it was learned.

Split horizon is a method that controls the sending of EIGRP update and query packets. When you enable split horizon on an interface, Cisco NX-OS does not send update and query packets for destinations that were learned from this interface. Controlling update and query packets in this manner reduces the possibility of routing loops.

Split horizon with poison reverse configures EIGRP to advertise a learned route as unreachable back through that the interface that EIGRP learned the route from.

EIGRP uses split horizon or split horizon with poison reverse in the following scenarios:

  • Exchanging topology tables for the first time between two routers in startup mode.

  • Advertising a topology table change.

  • Sending a query message.

By default, the split horizon feature is enabled on all interfaces.

Virtualization Support

Cisco NX-OS supports multiple instances of the EIGRP protocol that runs on the same system. EIGRP supports Virtual Routing and Forwarding instances (VRFs). By default, Cisco NX-OS places you in the default VRF unless you specifically configure another VRF.

By default, every instance uses the same system router ID. You can optionally configure a unique router ID for each instance.

Prerequisites for EIGRP

EIGRP has the following prerequisites:

Guidelines and Limitations for EIGRP

EIGRP has the following configuration guidelines and limitations:

  • A metric configuration (either through the default-metric configuration option or through a route map) is required for redistribution from any other protocol, connected routes, or static routes (see Configuring Route Policy Manager).

  • Cisco NX-OS EIGRP is compatible with EIGRP in the Cisco IOS software.

  • Do not change the metric weights without a good reason. If you change the metric weights, you must apply the change to all EIGRP routers in the same autonomous system.

  • Consider using stubs for larger networks.

  • Avoid redistribution between different EIGRP autonomous systems because the EIGRP vector metric will not be preserved.

  • The no ip next-hop-self command does not guarantee reachability of the next hop.

  • The ip passive-interface eigrp command suppresses neighbors from forming.

  • Cisco NX-OS does not support IGRP or connecting IGRP and EIGRP clouds.

  • Autosummarization is not enabled by default.

  • Cisco NX-OS supports only IP.


Note

If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Default Settings for EIGRP

Table below lists the default settings for EIGRP parameters.

Table 1. Default EIGRP Parameters

Parameters

Default

Administrative distance

  • Internal routes—90

  • External routes—170

Bandwidth percent

50 percent

Default metric for redistributed routes

  • bandwidth—100000 Kb/s

  • delay—100 (10 microsecond units)

  • reliability—255

  • loading—1

  • MTU—1500

EIGRP feature

Disabled

Hello interval

5 seconds

Hold time

15 seconds

Equal-cost paths

8

Metric weights

1 0 1 0 0

Next-hop address advertised

IP address of local interface

Redistribution

Disabled

Split horizon

Enabled

Configuring Basic EIGRP

Enabling the EIGRP Feature

You must enable the EIGRP feature before you can configure EIGRP.

SUMMARY STEPS

  1. configure terminal
  2. feature eigrp
  3. (Optional) show feature
  4. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

feature eigrp

Example:

switch(config)# feature eigrp

Enables the EIGRP feature.

Step 3

(Optional) show feature

Example:

switch(config)# show feature
 (Optional)

Displays information about enabled features.

Step 4

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
 (Optional)

Saves this configuration change.

Example

Use the no feature eigrp command to disable the EIGRP feature and remove all associated configuration.

Command

Purpose

no feature eigrp

Example:

switch(config)# no feature eigrp

Disables the EIGRP feature and removes all associated configuration.

Creating an EIGRP Instance

You can create an EIGRP instance and associate an interface with that instance. You assign a unique autonomous system number for this EIGRP process (see the Autonomous Systems section). Routes are not advertised or accepted from other autonomous systems unless you enable route redistribution.

Before you begin

Ensure that you have enabled the EIGRP feature (see the Enabling the EIGRP Feature section).

EIGRP must be able to obtain a router ID (for example, a configured loopback address) or you must configure the router ID option.

If you configure an instance tag that does not qualify as an AS number, you must configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

SUMMARY STEPS

  1. configure terminal
  2. router eigrp instance-tag
  3. (Optional) autonomous-system as-number
  4. (Optional) log-adjacency-changes
  5. log-neighbor-warnings [ seconds ]
  6. interface interface-type slot/port
  7. no switchport
  8. ip router eigrp instance-tag
  9. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1
switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

Step 3

(Optional) autonomous-system as-number

Example:

switch(config-router)# autonomous-system 33
 (Optional)

Configures a unique AS number for this EIGRP instance. The range is from 1 to 65535.

Step 4

(Optional) log-adjacency-changes

Example:

switch(config-router)# log-adjacency-changes
 (Optional)

Generates a system message whenever an adjacency changes state. This command is enabled by default.

Step 5

log-neighbor-warnings [ seconds ]

Example:

switch(config-router)# log-neighbor-warnings

Generates a system message whenever a neighbor warning occurs. You can configure the time between warning messages, from 1 to 65535, in seconds. The default is 10 seconds. This command is enabled by default.

Step 6

interface interface-type slot/port

Example:

switch(config-router)# interface ethernet 1/2
switch(config-if)#

Enters interface configuration mode. Use ? to determine the slot and port ranges.

Step 7

no switchport

Example:

switch(config-if)# no switchport

Configures the interface as a Layer 3 routed interface.

Step 8

ip router eigrp instance-tag

Example:

switch(config-if)# ip router eigrp Test1

Associates this interface with the configured EIGRP process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 9

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
 (Optional)

Saves this configuration change.

Example

Use the no router eigrp command to remove the EIGRP process and the associated configuration.

Command

Purpose

no router eigrp instance-tag

Example:

switch(config)# no router eigrp Test1

Deletes the EIGRP process and all associated configuration.

Note

You should also remove any EIGRP commands configured in interface mode if you remove the EIGRP process.

This example shows how to create an EIGRP process and configure an interface for EIGRP:

switch# configure terminal
switch(config)# router eigrp Test1
switch(config)# i nterface ethernet 1/2
switch(config-if)# no switchport
switch(config-if)# ip router eigrp Test1
switch(config-if)# no shutdown
switch(config-if)# copy running-config startup-config

For more information about other EIGRP parameters, see the Configuring Advanced EIGRP section.

Restarting an EIGRP Instance

You can restart an EIGRP instance. This clears all neighbors for the instance.

To restart an EIGRP instance and remove all associated neighbors, use the following commands:

Command

Purpose

flush-routes

Example:

switch(config)# flush-routes

Flushes all EIGRP routes in the unicast RIB when this EIGRP instance restarts.

restart eigrp instance-tag

Example:

switch(config)# restart eigrp Test1

Restarts the EIGRP instance and removes all neighbors. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Shutting Down an EIGRP Instance

You can gracefully shut down an EIGRP instance. This action moves all routes and adjacencies but preserves the EIGRP configuration.

To disable an EIGRP instance, use the following command in router configuration mode:

Command

Purpose

shutdown

Example:

switch(config-router)# shutdown

Disables this instance of EIGRP. The EIGRP router configuration remains.

Configuring a Passive Interface for EIGRP

You can configure a passive interface for EIGRP. A passive interface does not participate in EIGRP adjacency but the network address for the interface remains in the EIGRP topology table.

To configure a passive interface for EIGRP, use the following command in interface configuration mode:

Command

Purpose

ip passive-interface eigrp instance-tag

Suppresses EIGRP hellos, which prevents neighbors from forming and sending routing updates on an EIGRP interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Shutting Down EIGRP on an Interface

You can gracefully shut down EIGRP on an interface. This action removes all adjacencies and stops EIGRP traffic on this interface but preserves the EIGRP configuration.

To disable EIGRP on an interface, use the following command in interface configuration mode:

Command

Purpose

ip eigrp instance-tag shutdown

Example:

switch(config-router)# ip eigrp Test1 shutdown

Disables EIGRP on this interface. The EIGRP interface configuration remains. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Configuring Advanced EIGRP

This section includes the following topics:

Configuring Authentication in EIGRP

You can configure authentication between neighbors for EIGRP. See the Authentication section.

You can configure EIGRP authentication for the EIGRP process or for individual interfaces. Interface EIGRP authentication configuration overrides the EIGRP process-level authentication configuration.

Before you begin

Ensure that you have enabled the EIGRP feature (see the Enabling the EIGRP Feature section).

Ensure that all neighbors for an EIGRP process share the same authentication configuration, including the shared authentication key.

Create the key-chain for this authentication configuration. See the Cisco Nexus 3548 Switch NX-OS Security Configuration Guide.

SUMMARY STEPS

  1. configure terminal
  2. router eigrp instance-tag
  3. address-family ipv4 unicast
  4. authentication key-chain key-chain
  5. authentication mode md5
  6. interface interface-type slot/port
  7. no switchport
  8. ip router eigrp instance-tag
  9. ip authentication key-chain eigrp instance-tag key-chain
  10. ip authentication mode eigrp instance-tag md5
  11. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1
switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

Step 3

address-family ipv4 unicast

Example:

switch(config-router)# address-family ipv4 unicast
switch(config-router-af)#

Enters the address-family configuration mode. This command is optional for IPv4.

Step 4

authentication key-chain key-chain

Example:

switch(config-router-af)# authentication key-chain routeKeys

Associates a key chain with this EIGRP process for this VRF. The key chain can be any case-sensitive, alphanumeric string up to 20 characters.

Step 5

authentication mode md5

Example:

switch(config-router-af)# authentication mode md5

Configures MD5 message digest authentication mode for this VRF.

Step 6

interface interface-type slot/port

Example:

switch(config-router-af) interface ethernet 1/2
switch(config-if)#

Enters interface configuration mode. Use ? to find the supported interfaces.

Step 7

no switchport

Example:

switch(config-if)# no switchport

Configures the interface as a Layer 3 routed interface.

Step 8

ip router eigrp instance-tag

Example:

switch(config-if)# ip router eigrp Test1

Associates this interface with the configured EIGRP process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 9

ip authentication key-chain eigrp instance-tag key-chain

Example:

switch(config-if)# ip authentication key-chain eigrp Test1 routeKey

Associates a key chain with this EIGRP process for this interface. This configuration overrides the authentication configuration set in the router VRF mode.

The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 10

ip authentication mode eigrp instance-tag md5

Example:

switch(config-if)# ip authentication mode eigrp Test1 md5

Configures the MD5 message digest authentication mode for this interface. This configuration overrides the authentication configuration set in the router VRF mode.

The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 11

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
 (Optional)

Saves this configuration change.

Example

This example shows how to configure MD5 message digest authentication for EIGRP over Ethernet interface 1/2:

switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# exit
switch(config)# interface ethernet 1/2
switch(config-if)# no switchport
switch(config-if)# ip router eigrp Test1
switch(config-if)# ip authentication key-chain eigrp Test1 routeKeys
switch(config-if)# ip authentication mode eigrp Test1 md5
switch(config-if)# copy running-config startup-config

Configuring EIGRP Stub Routing

To configure a router for EIGRP stub routing, use the following command in address-family configuration mode:

Command

Purpose

stub [ direct | receive-only | redistributed [ direct ] leak-map map-name ]

Example:

switch(config-router-af)# eigrp stub redistributed

Configures a remote router as an EIGRP stub router. The map name can be any case-sensitive, alphanumeric string up to 20 characters.

This example shows how to configure a stub router to advertise directly connected and redistributed routes:

switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# stub direct redistributed
switch(config-router-af)# copy running-config startup-config

Use the show ip eigrp neighbor detail command to verify that a router has been configured as a stub router. The last line of the output shows the stub status of the remote or spoke router. This example shows the output from the show ip eigrp neighbor detail command: 

Router# show ip eigrp neighbor detail
IP-EIGRP neighbors for process 201
H Address Interface Hold Uptime SRTT RTO Q Seq Type
(sec) (ms) Cnt Num
0 10.1.1.2 Se3/1 11 00:00:59 1 4500 0 7
Version 12.1/1.2, Retrans: 2, Retries: 0
Stub Peer Advertising ( CONNECTED SUMMARY) Routes

Configuring a Summary Address for EIGRP

You can configure a summary aggregate address for a specified interface. If any more specific routes are in the routing table, EIGRP will advertise the summary address out the interface with a metric equal to the minimum of all more specific routes. See the Route Summarization section.

To configure a summary aggregate address, use the following command in interface configuration mode:

Command

Purpose

ip summary-address eigrp instance-tag ip-prefix/length [ distance | leak-map map-name ]

Example:

switch(config-if)# ip summary-address eigrp Test1 192.0.2.0/8

Configures a summary aggregate address as either an IP address and network mask, or an IP prefix/length. The instance tag and map name can be any case-sensitive, alphanumeric string up to 20 characters.

You can optionally configure the administrative distance for this aggregate address. The default administrative distance is 5 for aggregate addresses.

This example causes EIGRP to summarize network 192.0.2.0 out Ethernet 1/2 only:

switch(config)# interface ethernet 1/2
switch(config-if)# no switchport
switch(config-if)# ip summary-address eigrp Test1 192.0.2.0 255.255.255.0

Redistributing Routes into EIGRP

Ensure that you have enabled the EIGRP feature (see the Enabling the EIGRP Feature section).

You must configure the metric (either through the default-metric configuration option or through a route map) for routes redistributed from any other protocol.

You must create a route map to control the types of routes that are redistributed into EIGRP. See Configuring Route Policy Manager.

Before you begin

You can redistribute routes in EIGRP from other routing protocols.

SUMMARY STEPS

  1. configure terminal
  2. router eigrp instance-tag
  3. address-family ipv4 unicast
  4. redistribute { bgp as | { eigrp | ospf | ospfv3 | rip } instance-tag | direct | static } route-map name
  5. default-metric bandwidth delay reliability loading mtu
  6. show ip eigrp route-map statistics redistribute
  7. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1
switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

Step 3

address-family ipv4 unicast

Example:

switch(config-router)# address-family ipv4 unicast
switch(config-router-af)#

Enters the address-family configuration mode. This command is optional for IPv4.

Step 4

redistribute { bgp as | { eigrp | ospf | ospfv3 | rip } instance-tag | direct | static } route-map name

Example:

switch(config-router-af)# redistribute bgp 100 route-map BGPFilter

Injects routes from one routing domain into EIGRP. The instance tag and map name can be any case-sensitive, alphanumeric string up to 20 characters.

Step 5

default-metric bandwidth delay reliability loading mtu

Example:

switch(config-router-af)# default-metric 500000 30 200 1 1500

Sets the metrics assigned to routes learned through route redistribution. The default values are as follows:

  • bandwidth—100000 Kb/s

  • delay—100 (10 microsecond units)

  • reliability—255

  • loading—1

  • MTU—1492

Step 6

show ip eigrp route-map statistics redistribute

Example:

switch(config-router-af)# show ip eigrp route-map statistics redistribute bgp

Displays information about EIGRP route map statistics.

Step 7

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
 (Optional)

Saves this configuration change.

Example

This example shows how to redistribute BGP into EIGRP for IPv4:

switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# redistribute bgp 100 route-map BGPFilter
switch(config-router)# default-metric 500000 30 200 1 1500
switch(config-router)# copy running-config startup-config

Limiting the Number of Redistributed Routes

Route redistribution can add many routes to the EIGRP route table. You can configure a maximum limit to the number of routes accepted from external protocols. EIGRP provides the following options to configure redistributed route limits:

  • Fixed limit—Logs a message when EIGRP reaches the configured maximum. EIGRP does not accept any more redistributed routes. You can optionally configure a threshold percentage of the maximum where EIGRP will log a warning when that threshold is passed.

  • Warning only—Logs a warning only when EIGRP reaches the maximum. EIGRP continues to accept redistributed routes.

  • Withdraw—Start the timeout period when EIGRP reaches the maximum. After the timeout period, EIGRP requests all redistributed routes if the current number of redistributed routes is less than the maximum limit. If the current number of redistributed routes is at the maximum limit, EIGRP withdraws all redistributed routes. You must clear this condition before EIGRP accepts more redistributed routes. You can optionally configure the timeout period.

Before you begin

Be sure the EIGRP feature is enabled (see the Enabling the EIGRP Feature section).

SUMMARY STEPS

  1. configure terminal
  2. router eigrp instance-tag
  3. redistribute { bgp id | direct | eigrp id | ospf id | rip id | static } route-map map-name
  4. redistribute maximum-prefix max [ threshold ] [ warning-only | withdraw [ num-retries timeout ]]
  5. (Optional) show running-config eigrp
  6. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1
switch(config-router)#

Creates a new EIGRP process with the configured instance tag.

Step 3

redistribute { bgp id | direct | eigrp id | ospf id | rip id | static } route-map map-name

Example:

switch(config-router)# redistribute bgp route-map FilterExternalBGP

Redistributes the selected protocol into EIGRP through the configured route map.

Step 4

redistribute maximum-prefix max [ threshold ] [ warning-only | withdraw [ num-retries timeout ]]

Example:

switch(config-router)# redistribute maximum-prefix 1000 75 warning-only

Specifies a maximum number of prefixes that EIGRP will distribute. The range is from 0 to 65536. Optionally specifies the following:

  • threshold —Percent of maximum prefixes that will trigger a warning message.

  • warning-only —Logs an warning message when the maximum number of prefixes is exceeded.

  • withdraw —Withdraws all redistributed routes. Optionally tries to retrieve the redistributed routes. The num-retries range is from 1 to 12. The timeout is from 60 to 600 seconds. The default is 300 seconds. Use clear ip eigrp redistribution if all routes are withdrawn.

Step 5

(Optional) show running-config eigrp

Example:

switch(config-router)# show running-config eigrp
 (Optional)

Displays the EIGRP configuration.

Step 6

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
 (Optional)

Saves this configuration change.

Example

This example shows how to limit the number of redistributed routes into EIGRP:

switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# redistribute bgp route-map FilterExternalBGP
switch(config-router)# redistribute maximum-prefix 1000 75

Configuring Load Balancing in EIGRP

You can configure load balancing in EIGRP. You can configure the number of Equal Cost Multiple Path (ECMP) routes using the maximum paths option.

Before you begin

Ensure that you have enabled the EIGRP feature. See the Enabling the EIGRP Feature section.

SUMMARY STEPS

  1. configure terminal
  2. router eigrp instance-tag
  3. address-family ipv4 unicast
  4. maximum-paths num-paths
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1
switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an autonomous system number, you must use the autonomous-system command to configure the autonomous system number explicitly or this EIGRP instance will remain in the shutdown state.

Step 3

address-family ipv4 unicast

Example:

switch(config-router)# address-family ipv4 unicast
switch(config-router-af)#

Enters the address-family configuration mode. This command is optional for IPv4.

Step 4

maximum-paths num-paths

Example:

switch(config-router-af)# maximum-paths 5

Sets the number of equal cost paths that EIGRP will accept in the route table. The range is from 1 to 32. The default is 8.

Step 5

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
 (Optional)

Saves this configuration change.

Example

This example shows how to configure equal cost load balancing for EIGRP over IPv4 with a maximum of six equal cost paths:

switch# configure terminal
switch(config)# router eigrp Test1
switch(config-router)# maximum-paths 6
switch(config-router)# copy running-config startup-config

Adjusting the Interval Between Hello Packets and the Hold Time

You can adjust the interval between hello messages and the hold time.

By default, hello messages are sent every 5 seconds. The hold time is advertised in hello messages and indicates to neighbors the length of time that they should consider the sender valid. The default hold time is three times the hello interval, or 15 seconds.

To change the interval between hello packets, use the following command in interface configuration mode:

Command

Purpose

ip hello-interval eigrp instance-tag seconds

Example:

switch(config-if)# ip hello-interval eigrp Test1 30

Configures the hello interval for an EIGRP routing process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The range is from 1 to 65535 seconds. The default is 5.

On very congested and large networks, the default hold time might not be sufficient time for all routers to receive hello packets from their neighbors. In this case, you might want to increase the hold time.

To change the hold time, use the following command in interface configuration mode:

Command

Purpose

ip hold-time eigrp instance-tag seconds

Example:

switch(config-if)# ip hold-time eigrp Test1 30

Configures the hold time for an EIGRP routing process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The range is from 1 to 65535.

Use the show ip eigrp interface detail command to verify timer configuration.

Disabling Split Horizon

You can use split horizon to block route information from being advertised by a router out of any interface from which that information originated. Split horizon usually optimizes communications among multiple routing switches, particularly when links are broken.

By default, split horizon is enabled on all interfaces.

To disable split horizon, use the following command in interface configuration mode:

Command

Purpose

no ip split-horizon eigrp instance-tag

Example:

switch(config-if)# no ip split-horizon eigrp Test1

Disables split horizon.

Tuning EIGRP

You can configure optional parameters to tune EIGRP for your network.

You can configure the following optional parameters in address-family configuration mode:

Command

Purpose

default-information originate [ always | route-map map-name ]

Example:

switch(config-router-af)# default-information originate always

Originates or accepts the default route with prefix 0.0.0.0/0. When a route map is supplied, the default route is originated only when the route map yields a true condition. The map name can be any case-sensitive, alphanumeric string up to 20 characters.

distance internal external

Example : 

switch(config-router-af)# distance 25 100

Configures the administrative distance for this EIGRP process. The range is from 1 to 255. The internal value sets the distance for routes learned from within the same autonomous system (the default value is 90). The external value sets the distance for routes learned from an external autonomous system (the default value is 170).

metric maximum-hops hop-count

Example:

switch(config-router-af)# metric maximum-hops 70

Sets maximum allowed hops for an advertised route. Routes over this maximum are advertised as unreachable. The range is from 1 to 255. The default is 100.

metric weights tos k1 k2 k3 k4 k5

Example:

switch(config-router-af)# metric weights 0 1 3 2 1 0

Adjusts the EIGRP metric or K value. EIGRP uses the following formula to determine the total metric to the network:

metric = [k1*bandwidth + (k2*bandwidth)/(256 – load) + k3*delay] * [k5/(reliability + k4)]

Default values and ranges are as follows:

  • TOS—0. The range is from 0 to 8.

  • k1—1. The range is from 0 to 255.

  • k2—0. The range is from 0 to 255.

  • k3—1. The range is from 0 to 255.

  • k4—0. The range is from 0 to 255.

  • k5—0. The range is from 0 to 255.

timers active-time { time-limit | disabled }

Example : 

switch(config-router-af)# timers active-time 200

Sets the time the router waits in minutes (after sending a query) before declaring the route to be stuck in the active (SIA) state. The range is from 1 to 65535. The default is 3.

You can configure the following optional parameters in interface configuration mode:

Command

Purpose

ip bandwidth eigrp instance-tag bandwidth

Example:

switch(config-if)# ip bandwidth eigrp Test1 30000

Configures the bandwidth metric for EIGRP on an interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The bandwidth range is from 1 to 2,560,000,000 Kb/s.

ip bandwidth-percent eigrp instance-tag percent

Example:

switch(config-if)# ip bandwidth-percent eigrp Test1 30

Configures the percentage of bandwidth that EIGRP might use on an interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

The percent range is from 0 to 100. The default is 50.

no ip delay eigrp instance-tag delay

Example:

switch(config-if)# ip delay eigrp Test1 100

Configures the delay metric for EIGRP on an interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters. The delay range is from 1 to 16777215 (in tens of microseconds).

ip distribute-list eigrp instance-tag { prefix-list name | route-map name} { in | out }

Example:

switch(config-if)# ip distribute-list eigrp Test1 route-map EigrpTest in

Configures the route filtering policy for EIGRP on this interface. The instance tag, prefix list name, and route map name can be any case-sensitive, alphanumeric string up to 20 characters.

no ip next-hop-self eigrp instance-tag

Example:

switch(config-if)# ip next-hop-self eigrp Test1

Configures EIGRP to use the received next-hop address rather than the address for this interface. The default is to use the IP address of this interface for the next-hop address. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

ip offset-list eigrp instance-tag { prefix-list name | route-map name} { in | out } offset

Example:

switch(config-if)# ip offfset-list eigrp Test1 prefix-list EigrpList in

Adds an offset to incoming and outgoing metrics to routes learned by EIGRP. The instance tag, prefix list name, and route map name can be any case-sensitive, alphanumeric string up to 20 characters.

ip passive-interface eigrp instance-tag

Example:

switch(config-if)# ip passive-interface eigrp Test1

Suppresses EIGRP hellos, which prevents neighbors from forming and sending routing updates on an EIGRP interface. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Configuring Virtualization for EIGRP

You can create multiple VRFs and use the same or multiple EIGRP processes in each VRF. You assign an interface to a VRF.


Note

Configure all other parameters for an interface after you configure the VRF for an interface. Configuring a VRF for an interface deletes all other configuration for that interface.

Before you begin

Ensure that you have enabled the EIGRP feature (see the xrefEnabling the EIGRP Featuresection).

SUMMARY STEPS

  1. configure terminal
  2. vrf context vrf-name
  3. router eigrp instance-tag
  4. interface ethernet slot/port
  5. no switchport
  6. vrf member vrf-name
  7. ip router eigrp instance-tag
  8. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

vrf context vrf-name

Example:

switch(config)# vrf context RemoteOfficeVRF
switch(config-vrf)#

Creates a new VRF and enters VRF configuration mode. The VRN name can be any case-sensitive, alphanumeric string up to 20 characters.

Step 3

router eigrp instance-tag

Example:

switch(config)# router eigrp Test1
switch(config-router)#

Creates a new EIGRP process with the configured instance tag. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

If you configure an instance-tag that does not qualify as an AS number, you must use the autonomous-system command to configure the AS number explicitly or this EIGRP instance will remain in the shutdown state.

Step 4

interface ethernet slot/port

Example:

switch(config)# interface ethernet 1/2
switch(config-if)#

Enters interface configuration mode. Use ? to find the slot and port ranges.

Step 5

no switchport

Example:

switch(config-if)# no switchport

Configures the interface as a Layer 3 routed interface.

Step 6

vrf member vrf-name

Example:

switch(config-if)# vrf member RemoteOfficeVRF

Adds this interface to a VRF. The VRF name can be any case-sensitive, alphanumeric string up to 20 characters.

Step 7

ip router eigrp instance-tag

Example:

switch(config-if)# ip router eigrp Test1

Adds this interface to the EIGRP process. The instance tag can be any case-sensitive, alphanumeric string up to 20 characters.

Step 8

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
 (Optional)

Saves this configuration change.

Example

This example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal
switch(config)# vrf context NewVRF
switch(config-vrf)# router eigrp Test1
switch(config-router)# i nterface ethernet 1/2
switch(config-if)# no switchport
switch(config-if)# ip router eigrp Test1
switch(config-if)# vrf member NewVRF
switch(config-if)# copy running-config startup-config

Verifying the EIGRP Configuration

To display the EIGRP configuration information, perform one of the following tasks:

Command

Purpose

show ip eigrp [ instance-tag ]

Displays a summary of the configured EIGRP processes.

show ip eigrp [ instance-tag ] interfaces [ type number ] [ brief ] [ detail ]

Displays information about all configured EIGRP interfaces.

show ip eigrp instance-tag neighbors [ type number ]

Displays information about all the EIGRP neighbors. Use this command to verify the EIGRP neighbor configuration.

show ip eigrp [ instance-tag ] route [ ip-prefix/length ] [ active ] [ all-links ] [detail-links] [ pending ] [ summary ] [ zero-successors ] [ vrf vrf-name ]

Displays information about all the EIGRP routes.

show ip eigrp [ instance-tag ] topology [ ip-prefix/length ] [ active ] [ all-links ] [detail-links] [ pending ] [ summary ] [ zero-successors ] [ vrf vrf-name ]

Displays information about the EIGRP topology table.

show running-configuration eigrp

Displays the current running EIGRP configuration.

Displaying EIGRP Statistics

To display EIGRP statistics, use the following commands:

Command

Purpose

show ip eigrp [ instance-tag ] accounting [ vrf vrf-name ]

Displays accounting statistics for EIGRP.

show ip eigrp [ instance-tag ] route-map statistics redistribute

Displays redistribution statistics for EIGRP.

show ip eigrp [ instance-tag ] traffic [ vrf vrf-name ]

Displays traffic statistics for EIGRP.

Configuration Examples for EIGRP

This example shows how to configure EIGRP:

feature eigrp
interface ethernet 1/2
no switchport
ip address 192.0.2.55/24
ip router eigrp Test1
no shutdown
router eigrp Test1
router-id 192.0.2.1

Additional References

For additional information related to implementing EIGRP, see the following sections:

MIBs

MIBs

MIBs Link

CISCO-EIGRP-MIB

To locate and download MIBs, go to the following: MIB Locator.