Cisco NX-OS/IOS EIGRP Comparison

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Objective

This tech note outlines the main differences in Enhanced Interior Gateway Protocol (EIGRP) support between Cisco® NX-OS Software and Cisco IOS® Software. Sample configurations are included for Cisco NX-OS and Cisco IOS Software for some common features to demonstrate the similarities and differences. Please refer to the NX-OS documentation on Cisco.com for a complete list of supported features.


EIGRP Overview

EIGRP is a Cisco proprietary hybrid distance vector routing protocol used to exchange network reachability information within an autonomous system.


Important Cisco NX-OS and Cisco IOS Software Differences

In Cisco NX-OS:

  • The EIGRP protocol supports In-Service-Software-Upgrades (ISSU) if two supervisors are present in a chassis (Graceful Restart must be enabled).
  • EIGRP command-line interface (CLI) configuration and verification commands are not available until you enable the EIGRP feature with the feature eigrp command.
  • The EIGRP protocol requires the Enterprise Services license.
  • Only the Internet Protocol (IP) is supported. Cisco IOS Software supports IP, IPX, and Appletalk.
  • The EIGRP instance can consist of 20 characters. Cisco IOS Software supports numbers 1- 65536.
  • Eight equal-cost paths are supported by default; Cisco NX-OS supports up to 16.
  • Unequal cost load balancing is not supported. In Cisco IOS Software, unequal cost load balancing can be configured under an EIGRP routing instance using the variance command with an associated multiplier to select the next hop feasible successors for an IP route.
  • Route auto-summarization is disabled by default and cannot be manually configured.
  • Networks and interfaces are added to an EIGRP instance under the interface configuration mode.
  • If a router ID is not manually configured, the loopback 0 IP address is always preferred. If loopback 0 does not exist, Cisco NX-OS selects the IP address for the first loopback interface in the configuration. If no loopback interfaces exist, Cisco NX-OS selects the IP address for the first physical interface in the configuration.
  • A default route can be generated with the default-information originate command, whereas Cisco IOS Software requires additional CLI commands to achieve similar results.
  • When interface authentication is configured, the EIGRP key is encrypted with Data Encryption Standard 3 (3DES) in the configuration. Cisco IOS Software requires the service password command.
  • Distribute-lists used to filter routes from routing updates are applied under the interface with the ip distribute-list eigrp command, as opposed to under the EIGRP router instance.
  • Maximum prefix thresholds (warning and withdraw) can be configured for redistributed routes using the redistribute maximum-prefix routing instance command. Cisco IOS Software does not have the ability to set maximum prefix thresholds for redistributed routes.
  • A route-map is always required when redistributing routes into an EIGRP instance. In Cisco IOS Software, a route-map is optional.


Things You Should Know

The following list provides some additional facts about Cisco NX-OS that should be helpful when designing, configuring, and maintaining an EIGRP network.


  • Four EIGRP instances can be configured per virtual device context (VDC).
  • Numerous Virtual Route Forwarding (VRF) instances can be associated with an EIGRP instance.
  • If the feature eigrp command is removed, all relevant EIGRP configuration information is also removed.
  • The shutdown command can be used to gracefully disable an EIGRP instance while retaining the configuration. This feature can also be applied per interface with the ip eigrp <instance> shutdown command.
  • An EIGRP instance can be restarted with the restart eigrp <instance> Exec command.
  • Graceful restart is enabled by default (It needs to be enabled in order to perform an ISSU upgrade).
  • Multiple EIGRP instances can be configured on the same interface.
  • Secondary IP addresses are advertised by default and cannot be suppressed per interface.
  • The show running-config eigrp command displays the current EIGRP configuration.
  • EIGRP supports Bidirectional Forwarding Detection (BFD), which can be configured to reduce network convergence time to less than one second.


Configuration Comparison

The following sample code shows configuration similarities and differences between the Cisco NX-OS and Cisco IOS Software CLIs. There are three significant differences: Cisco NX-OS allows EIGRP to be enabled and disabled globally, and it has a more interface-centric configuration that makes it easier to read. In addition, Cisco NX-OS has the capability to generate a default route, whereas Cisco IOS Software requires additional CLI commands to achieve similar results.


Cisco IOS CLI Cisco NX-OS CLI
Enabling the EIGRP Feature
Cisco IOS Software does not have the ability to enable or disable EIGRP. feature eigrp
Configuring an EIGRP Instance and Router ID
router eigrp 10

eigrp router-id 192.168.1.1

router eigrp 10

router-id 192.168.1.1

Associating a Network with an EIGRP Instance
router eigrp 10

network 192.168.10.0

interface Ethernet2/1

ip address 192.168.10.1/24

ip router eigrp 10

Configuring a Passive Interface
router eigrp 10

network 192.168.10.0 passive-interface GigabitEthernet2/1

interface Ethernet2/1

ip address 192.168.10.1/24

ip router eigrp 10

ip passive-interface eigrp 10

Configuring Interface Authentication (MD5)
key chain eigrp-key

key 1 key-string cisco123


interface GigabitEthernet2/1 ip address 192.168.10.1 255.255.255.0 ip authentication mode eigrp 10 md5 ip authentication key-chain eigrp 10 eigrp-key

key chain eigrp-key

key 1 key-string 7 070c285f4d06485744


interface Ethernet2/1

ip address 192.168.10.1/24

ip router eigrp 10

ip authentication mode eigrp 10 md5

ip authentication key-chain eigrp 10 eigrp-key

Configuring an EIGRP Distribution List to Filter Routes
ip prefix-list eigrp-10-list seq 5 permit 159.142.1.0/24


router eigrp 10

network 192.168.10.0

distribute-list prefix eigrp-10-list out GigabitEthernet2/1

ip prefix-list eigrp-10-list seq 5 permit 159.142.1.0/24


interface Ethernet2/1

ip address 192.168.10.1/24

ip router eigrp 10

ip distribute-list eigrp 10 prefix-list eigrp-10-list out

Configuring Route Summarization
interface GigabitEthernet2/1

ip address 192.168.10.1 255.255.255.0

ip summary-address eigrp 10 159.142.0.0 255.255.0.0 5

interface Ethernet2/1

ip address 192.168.10.1/24

ip router eigrp 10

ip summary-address eigrp 10 159.142.0.0/16

Generating A Default Route (Conditional)
Cisco IOS Software doesn’t have the same CLI to generate a default route, but redistribution or the ip summary address command can be used to achieve similar results. router eigrp 10

default-information originate

Configuring Route Redistribution (Permit all Static Routes)
router eigrp 10

redistribute static

router eigrp 10

redistribute static route-map static-to-eigrp


route-map static-to-eigrp permit 10

Configuring a VRF Instance for EIGRP Routing
router eigrp 10

address-family ipv4 vrf customer-a autonomous-system 20

router eigrp 10

vrf customer-a

autonomous-system 20



Verification Command Comparison

The following table compares some useful show commands for verifying and troubleshooting an EIGRP network configuration.


Cisco NX-OS EIGRP Cisco IOS Software EIGRP Command Description
show ip eigrp - Displays global EIGRP information for all instances
show ip eigrp <instance> show ip eigrp <#> Displays global EIGRP information for a specific instance
show ip eigrp accounting show ip eigrp accounting Displays the number of prefixes that each neighbor advertised
show ip eigrp interfaces show ip eigrp interfaces Displays interfaces configured for EIGRP
show ip eigrp interfaces detail show ip eigrp interfaces detail Displays detailed interface information
show ip eigrp neighbors show ip eigrp neighbors Displays currently connected neighbors
show ip eigrp neighbors detail show ip eigrp neighbors detail Displays connected neighbors and associated details
show ip eigrp route - Displays EIGRP routes
show ip eigrp route-map statistics redistribute <protocol> - Displays statistics for redistributed routes per protocol
show ip eigrp topology show ip eigrp topology Displays the EIGRP topology table
show ip eigrp traffic show ip eigrp traffic Displays statistics related to EIGRP
show ip eigrp vrf show ip eigrp vrf Displays VRF information for a specified VRF instance

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