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EIGRP within NX-OS is compatible with EIGRP on IOS devices enabling a smooth inte-gration of Nexus equipment with existing gear. Configuring EIGRP within NX-OS will be similar, yet distinctly different in some aspects to traditional IOS configuration. These differences will be highlighted throughout the section.

Enabling EIGRP is a multistep process that will be covered in detail. The following is a quick listing of steps to enable a basic configuration of EIGRP:

Step 1. Enable EIGRP.

Step 2. Configure the EIGRP routing process.

Step 3. Assign interfaces to the instance tag.

Step 4. Configure passive interfaces if necessary.

Step 5. Configure network summarization.

Step 6. Configure the redistribution of other protocols if necessary.

Step 7. Verify EIGRP operation.

The first step to configure EIGRP is to enable it in global configuration mode using the feature command, as demonstrated in Example 3-2. With the modular nature of NX-OS, using the feature command loads the EIGRP modular code into memory for execution.

Without the feature enabled, it would not be resident in memory.

Example 3-2 Enabling EIGRP

Congo# confi t

Enter configuration commands, one per line. End with CNTL/Z.

Congo(config)# feature eigrp Congo(config)# end

Congo# show run eigrp

!Command: show running-config eigrp

!Time: Tue Sep 29 16:03:10 2009 version 4.2(2a)

feature eigrp

As with IOS-based EIGRP configuration, the next step is to configure the EIGRP routing process, as demonstrated in Example 3-3. In NX-OS, you configure an instance tag for the process. Traditionally in IOS this would be the autonomous system (AS) number. In NX-OS the instance tag can be the AS, but additionally the instance tag can be up to 20 case-sensitive alphanumeric characters.

Example 3-3 Creating an EIGRP Instance with a Numeric Tag

Congo# confi t

100 NX-OS and Cisco Nexus Switching: Next-Generation Data Center Architectures

Enter configuration commands, one per line. End with CNTL/Z.

Congo(config)# router eigrp 200 Congo(config-router)# exit Congo(config)# show run eigrp

!Command: show running-config eigrp

!Time: Tue Sep 29 16:05:21 2009 version 4.2(2a)

feature eigrp router eigrp 200

Example 3-4 shows an alphanumeric string for the tag.

Example 3-4 Creating an EIGRP Instance with an Alphanumeric String

Congo# confi t

Enter configuration commands, one per line. End with CNTL/Z.

Congo(config)# router eigrp DataCenter1 Congo(config)# show run eigrp

!Command: show running-config eigrp

!Time: Tue Sep 29 16:11:05 2009 version 4.2(2a)

feature eigrp

router eigrp DataCenter1

Note that when using an instance tag that cannot qualify as an AS number, use the autonomous-system as-number command to configure the AS; otherwise, EIGRP remains shut down.

Example 3-5 shows how to configure an AS number under an EIGRP process that uses an alphanumeric tag.

Example 3-5 Configuring EIGRP with an Autonomous System Number

Congo# confi t

Enter configuration commands, one per line. End with CNTL/Z.

Congo(config)# router eigrp DataCenter1 Congo(config-router)# autonomous-system 100 Congo(config-router)# exit

Congo(config)# show run eigrp

!Command: show running-config eigrp

!Time: Tue Sep 29 16:11:05 2009 version 4.2(2a)

Chapter 3: Layer 3 Support and Configurations 101

feature eigrp

router eigrp DataCenter1 autonomous-system 100

With EIGRP configured as a feature and assigned an autonomous system ID, the next step is to assign interfaces to the instance tag, as demonstrated in Example 3-6. This advertises the IP subnet in EIGRP and enables the capability for neighbor adjacencies to be formed.

Note that this is different from traditional IOS configuration where you configure a network statement under the routing process, and then, in turn, any interface on the router that fell within that network range was advertised. The approach taken in NX-OS is much more granular and enables additional levels of control over which networks are advertised.

Example 3-6 Adding an SVI to EIGRP with a Numeric Tag

Congo# confi t

Enter configuration commands, one per line. End with CNTL/Z.

Congo(config)# int vlan 10

Congo(config-if)# ip router eigrp 200 Congo(config-if)# show ip eigrp int vlan 10 IP-EIGRP interfaces for process 200 VRF default

Xmit Queue Mean Pacing Time Multicast Pending Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes Vlan10 0 0/0 0 0/10 0 0

Hello interval is 5 sec Holdtime interval is 15 sec Next xmit serial <none>

Un/reliable mcasts: 0/0 Un/reliable ucasts: 0/0 Mcast exceptions: 0 CR packets: 0 ACKs suppressed: 0 Retransmissions sent: 0 Out-of-sequence rcvd: 0 Authentication mode is not set

Example 3-7 shows how to add an SVI to EIGRP when using an alphanumeric tag.

Example 3-7 Adding an SVI to EIGRP with an Alphanumeric Tag

Congo# confi t

Enter configuration commands, one per line. End with CNTL/Z.

Congo(config)# int vlan 10

Congo(config-if)# ip router eigrp DataCenter1 Congo(config-if)# show ip eigrp int vlan 10 IP-EIGRP interfaces for process 100 VRF default

Xmit Queue Mean Pacing Time Multicast Pending

102 NX-OS and Cisco Nexus Switching: Next-Generation Data Center Architectures

Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes Vlan10 1 0/0 44 0/10 208 0

Hello interval is 5 sec Holdtime interval is 15 sec Next xmit serial <none>

Un/reliable mcasts: 0/1 Un/reliable ucasts: 2/2 Mcast exceptions: 0 CR packets: 0 ACKs suppressed: 1 Retransmissions sent: 0 Out-of-sequence rcvd: 0 Authentication mode is not set

In a data center’s distribution/aggregation layer, it is common to have multiple VLAN interfaces that, in turn, need to be advertised to the network at large. By default, when EIGRP is enabled on the VLAN interface, it sends and receives hellos. If a neighbor is detected, EIGRP attempts to form an adjacency. Although this default setup is wanted, there might be designs in which forming multiple EIGRP adjacencies between the same pair of switches is not wanted due to the potential impact of network convergence time and unnecessary duplicate next hops. In configurations such as this, use the passive-interface command, as demonstrated in Example 3-8. A passive passive-interface accomplishes the requirement of advertising the subnet via EIGRP, but also instructing the EIGRP process to not listen to hellos on the interfaces configured to be passive.

Example 3-8 Configuring a Passive Interface in EIGRP with a Numeric Tag

Congo# config t

Congo(config)# int vlan100

Congo(config-if)# ip passive-interface eigrp 200 Congo(config-if)# end

Example 3-9 shows how to configure a passive interface in EIGRP when using an alphanumeric tag.

Example 3-9 Configuring a Passive Interface in EIGRP with an Alphanumeric Tag

Congo# config t

Congo(config)# int vlan100

Congo(config-if)# ip passive-interface eigrp DataCenter1 Congo(config-if)# exit

Congo(config)# show run int vlan 100

!Command: show running-config interface Vlan100

!Time: Tue Sep 29 16:30:02 2009 version 4.2(2a)

interface Vlan100 no shutdown

description Server Subnet1

Chapter 3: Layer 3 Support and Configurations 103

ip address 10.10.100.2/24 ip router eigrp DataCenter1

ip passive-interface eigrp DataCenter1