Configure Nexus 7000 Series Switches for OTV Interoperability with ASRs

Introduction

This document describes how to configure Cisco Nexus 7000 Series switches so that they can be used with the Cisco Aggregated Services Router (ASR) in order to deploy Overlay Transport Virtualization (OTV) Layer 2 (L2) Data Center Interconnect technologies. 

Note: There are interoperability issues between the Nexus 7000 Series switches and the ASR in Versions 6.2(x) and later, which are resolved in accordance with Cisco bug ID CSCuo44890 on the Nexus switch.

Prerequisites

Requirements

Cisco recommends that you have knowledge of OTV configurations for both the Nexus and ASR platforms.

Components Used

The information in this document is based on these hardware and software versions:

• Cisco Nexus 7000 Series switches with M1 Series linecards that run software Version 6.2(12)
• Cisco 1000 Series ASRs that run Cisco IOS-XE^® Version 3.13 or 3.14

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Configure

Use the information in this section in order to configure the Nexus 7000 Series switch.

Note: Use the Command Lookup Tool (registered customers only) in order to obtain more information on the commands used in this section.

Network Diagram

The example that is provided in this document uses this topology:

 

Note: This diagram shows an adjacency server example; however, the interoperability issue also applies to scenarios with multicast configurations.

Configurations

This section provides the configurations for the Nexus and ASR devices.

N7K-1-OTV

N7K-1-OTV# show run otv

!Command: show running-config otv
!Time: Tue Dec 14 21:12:57 2010

version 6.2(12)
feature otv

otv site-vlan 3000

interface Overlay1
  otv join-interface Ethernet1/18
  otv extend-vlan 2001
  otv adjacency-server unicast-only
  no shutdown
otv-isis default
otv site-identifier 0x2

N7K-1-OTV#

N7K-2-OTV

N7K-2-OTV# show run otv

!Command: show running-config otv
!Time: Tue Dec 14 21:22:20 2010

version 6.2(12)
feature otv

otv site-vlan 3001

interface Overlay1
  otv join-interface Ethernet1/40
  otv extend-vlan 2001
  otv use-adjacency-server 10.1.1.2 unicast-only
  otv adjacency-server unicast-only
  no shutdown
otv-isis default
otv site-identifier 0x3

N7K-2-OTV#

ASR-OTV

ASR-OTV#show run
hostname ASR-OTV
!
otv site bridge-domain 1
!
otv site-identifier 0000.0000.0001
multilink bundle-name authenticated
!
interface Overlay1
 no ip address
 otv join-interface GigabitEthernet0/0/5
 otv use-adjacency-server 10.1.1.2 unicast-only
 otv adjacency-server unicast-only
 service instance 2001 ethernet
  encapsulation dot1q 2001
  bridge-domain 2001
 !
!
interface GigabitEthernet0/0/5
 description ****OTV Join interface****
 mtu 9216
 ip address 10.1.1.1 255.255.255.0
 shutdown
 negotiation auto
 cdp enable
!
interface GigabitEthernet0/0/6
 no ip address
 negotiation auto
 service instance 1 ethernet
  encapsulation untagged
  bridge-domain 1
 !
 service instance 2001 ethernet
  encapsulation dot1q 2001
  bridge-domain 2001
 !
ASR-OTV#

Verify

With the previous configurations in place, OTV adjacency should come up on all of the devices; however, you might observe that the OTV routes/ Media Access Control (MAC) addresses are only exchanged between Site 2 (N7K1) and Site 3 (N7K2). Examples are provided in the sections that follow.

Note: In this situation, no routes are exchanged between the ASR and the Nexus switches. However, routes are exchanged between the two Nexus switches.

N7K-1-OTV

N7K-1-OTV# show otv adjacency
Overlay Adjacency database

Overlay-Interface Overlay1  :

Hostname      System-ID       Dest Addr  Up Time   State
N7K-2-OTV     002a.6ae7.d442  10.1.1.3    1w4d      UP
ASR-OTV       88f0.774a.2800  10.1.1.1    00:00:22  UP

N7K-2-OTV

N7K-2-OTV# show otv adjacency
Overlay Adjacency database

Overlay-Interface Overlay1  :

Hostname      System-ID       Dest Addr  Up Time   State
N7K-1-OTV     002a.6ae7.d441  10.1.1.2    1w4d      UP
ASR-OTV       88f0.774a.2800  10.1.1.1    00:00:20  UP

ASR-OTV

ASR-OTV#show otv adjacency
Overlay Adjacency Database for overlay 1

Hostname     System-ID       Dest Addr  Site-ID         Up Time   State
N7K-2-OTV    002a.6ae7.d442  10.1.1.3    0000.0000.0003  00:00:13  UP
N7K-1-OTV    002a.6ae7.d441  10.1.1.2    0000.0000.0002  00:00:19  UP

Troubleshoot

In the situation that is described in the previous sections (even if it includes only one Nexus switch), you begin to observe tracebacks and Invalid Vlan Range error messages on the ASR:

*Apr  2 17:21:33.056: %CLNS-3-VLANRANGEERR:  (Overlay1): invalid vlan range received,
 begin 131137536, end 131137536, step 1
-Traceback= 1#4b5dcf00e7618154330c28bbb7d4cf9c  :7F681D4E7000+BD95181
:7F681D4E7000+BD95C59 :7F681D4E7000+BD94D0D :7F681D4E7000+8703A8A
:7F681D4E7000+86CB1B9 :7F681D4E7000+8705E11 :7F681D4E7000+87052C8
:7F681D4E7000+86F7EDF :7F681D4E7000+86F79DA :7F681D4E7000+86F794B
:7F681D4E7000+86DC3FF :7F681D4E7000+86FF620

The adjacencies remain up, but no routes are exchanged and the hosts cannot ping each other across the OTV. This occurs for all of the hosts between Site 1 and Site 2, as well as Site 1 and Site 3.

Cisco bug ID CSCuo44890 introduced a new CLI command (interop-enable) in the Nexus 7000 Series switch Versions 6.2(12) and later, which is required to be configured in order to ensure that the routes are exchanged between the sites.

Complete these steps in order to resolve the interoperability issue:

1. Shut down all overlay on all of the OTV Edge Devices (OEDs) that are configured on the switches.
   
   
2. Configure interop-enable under the otv-isis default for all of the Nexus 7000 Series OEDs.
   
   
3. Bring all overlays back online for all of the OEDs.

Here is an example:

N7K-1-OTV(config)# interface Overlay 1
N7K-1-OTV(config-if-overlay)# shut

N7K-2-OTV(config)# interface Overlay 1
N7K-2-OTV(config-if-overlay)# shut

N7K-1-OTV(config-if-overlay)# otv-isis default
N7K-1-OTV(config-router)# interop-enable
N7K-1-OTV(config-router)# end

N7K-2-OTV(config-if-overlay)# otv-isis default
N7K-2-OTV(config-router)# interop-enable
N7K-2-OTV(config-router)# end

N7K-1-OTV(config)# interface Overlay 1
N7K-1-OTV(config-if-overlay)#no shut

N7K-2-OTV(config)# interface Overlay 1
N7K-2-OTV(config-if-overlay)#no shut

You should now see route exchanges, and the hosts should be reachable across the OTV.

Note: This procedure must be completed for all of the Nexus 7000 Series OTV devices in the network. In this example, if you do not enable the interop-enable command on the N7K2-OTV, then the host behind it is not able to be reached from either of the hosts behind the ASR-OTV or N7K1-OTV devices.

Related Information

• ASR 1000 OTV Unicast Adjacency Server Configuration Example
• Cisco Nexus 7000 Series NX-OS OTV Configuration Guide
• Cisco bug ID CSCuo44890 - OTV FC: Inter-op between ASR1K and N7K failed
• Technical Support & Documentation - Cisco Systems