Trunking off a switch that is connected as a vPC peer

[Kyle Smith]

Hello,

Yesterday I ran into an issue in someones environment where they wanted to trunk a 2960 switch (Lets call it SwitchA) off of another 2960 (SwitchB) switch which was a vPC peer to a set of Nexus 5k's. When he did this, he noticed his phones were unable to communicate with the voice gateway. The same VLANs were allowed across the trunk from SwitchA to SwitchB and to the Nexus5K

When I moved SwitchA to its own port channel and vPC the voice traffic was able to communicate just fine. I am more concerned about this issue for learning/experience purposes. Has anyone run into a similar issue or know of a vPC rule that is preventing SwitchA from hanging off SwitchB? I have never seen a setup where someone wanted to do that when using vPC's but am still curious about that setup incase I run into it again in the future.

Thanks,

[Madhukrishnan Gopinathan Nair]

Hi kyle,

Were you sure you were allowing the same vlan over peer-link too?

Thanks,

Madhu.

[Kyle Smith]

Hey Madhu,

Thanks for your reply. 

Yes, I was allowing the same VLAN over the peer-link also. If I wasnt then all the other IDF switches would of had downed phones. The odd thing also is when SwitchA was trunked to SwitchB desktops had connectivity but phones didnt. I then SSH'd into SwitchA and tried pinging the gateway for VLAN 120 (Voice VLAN) and was able to hit the gateway and the phone system, showing I had connectivity. For some reason though, the handsets just werent finding the router.

[Bilal Nawaz]

was vpc peer-gateway configured on both sides (if they were the gateway?) It sounds similar to a problem I had couple months back, and figured that I had forgotten to put the peer-gateway command in.

[Kyle Smith]

Yes both sides of the Nexus had the peer-gateway command for the domain.

Maybe I am not explaining this properly. The nexus and every other IDF switch was working fine. There was just one IDF switch they wanted to piggy back off another IDF to the Nexus pair. I set that as a standard trunk between the two IDF's allowing the same VLANs that the vPC was expecting to see which included all the appropriate VLANs.