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:
- 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.
- 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.
- Route auto-summarization is disabled by default.
- 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.
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 disable an EIGRP instance while retaining the configuration. This feature can also be applied per interface with the ip eigrp <instance #> shutdown command.
- The show running-config eigrp command displays the current EIGRP configuration.
- An EIGRP instance can be restarted with the restart eigrp <instance #> command.
- Graceful restart (RFC 3623) is enabled by default.
- Multiple EIGRP instances can be configured on the same interface.
- Secondary IP addresses are advertised by default and cannot be suppressed per interface.
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
| key chain eigrp-key
key 1 key-string 7 070c285f4d06485744
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
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
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 |
|---|
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 | show ip eigrp <#> | Displays all EIGRP information for a specified process |
| 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 policy | - | Displays redistribution statistics for the specified protocol |
| show ip eigrp route | - | Displays EIGRP routes |
| 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 |
