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Cisco Nexus VPC Domain ID

April 4th, 2014

For the last 3 days, I’ve tried to configure vPC for a pair of Nexus 5548UP. No matter what I did, the pair just refused to connect and form vPC properly. So far I have tried:
- Upgrading to NX-OS version 6
- Upgrading to NX-OS version 7
- Restarting to factory default configs
- Restarting the switches many times
- Checking cables and connectors

The configurations I had for them were
1 diagram

Shared Config:

First switch

Second switch

And I kept getting this
2 vlan down

3 vpc bri

Do you see the problem? It turned out that’s because I used the same vPC Domain ID as my KeepAlive Port-Channel ID :101. A mistake that can be made easily in my effort of keeping the code clean.

I fixed it by changing everything I could about the configuration, eventually I changed the vPC domain ID and it works

Then I found this Cisco document:
vPC Domain ID Modification on an Active vPC Domain

The vPC peer devices use the vPC domain ID that you configure in order to automatically assign a unique vPC system MAC address. Each vPC domain has a unique MAC address that is used as a unique identifier for the specific vPC-related operations. However, the devices use the vPC system MAC addresses only for link-scope operations, such as LACP. Therefore, Cisco recommends that you create each vPC domain within the contiguous Layer 2 network with a unique domain ID.

Categories: Data Center, Networking