Nexus vPC and Routing

[Nathan Farrar]

Just looking for clarification on something I've noticed with a recent 5572UP installation I did. 

I was replacing an existing older 5K pair of switches. vPC is configured on them in a standard way. I also enabled EIGRP in order to allow it to peer with an upstream 4507 core switch. When looking at the EIGRP neighbor table, I noticed that not only was the new 5K peering with the upstream switch, it was also peering with itself. Each of the SVIs found a peer across the vPC peer link. Is this normal? I don't think it would cause an issue but for some reason I found that surprising since HSRP is being used. Looking for confirmation that this is normal.

[ADP_89]

Hello Nathan,

By saying "it was also peering with itself" do you actually mean it is peering with the other VPC peer? If not I don't really understand the topology, can you provide a quick diagram?

What version are you running on the new pair?

Thanks,

ADP

[Nathan Farrar]

Yes, you are correct. I wrote that too quickly. In my head I'm thinking of the pair as one switch which it is not.

[ADP_89]

No worries, what NxOs version are you running on the pair?

[Nathan Farrar]

7.3.3.

Wasn’t there some kind of bug with IGP peering over a L2 vPC with Nexus at one point on one version of code?

[ADP_89 · Accepted solution]

Actually version doesn't really matters on Nexus 5K.

Your behaviour is the normal one and it is supported by VPC best practices:

https://www.cisco.com/c/en/us/support/docs/ip/ip-routing/118997-technote-nexus-00.html

https://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf

--> Layer 3 and vPC Interactions: Supported Designs  Fig.53

HTH,

ADP

[Nathan Farrar]

Unfortunately, the PDF you linked to isn't available but I get the gist and I think I have a copy of it somewhere.

[ADP_89]

Link fixed, you should get to it now.

Cheers,

ADP