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vPC Peer-link is down whereas vPC peer is alive


I'm having a weird issue with vPC on N5K (5548P), running 5.0(3)N1(1) - Today I noticed that the N5K infrastructure had crashed. While looking into it, the problem was with vPC. What happened was that the switch noticed a loop, and brought down the vPC peer-link.

vPC domain id                 : 420

Peer status                     : peer link is down                              

vPC keep-alive status       : peer is alive            

So the Port channel holding the vPC peer-link was down, whereas the individual members in the link were up. I tried rebuilding the port-channel, rebuilding the vPC peer-link etc, but no luck. Each N5K was showing that it was to ROOT for ALL the VLANS (though originally each N5K was the root for one set of VLANS).

I had to shutdown the second N5K to have the environment up and running. Looking at the time when everything happened, the logs are of the form:

06:55:37   %STP-2-VPC_PEER_LINK_INCONSIST_BLOCK: vPC peer-link detected BPDU receive timeout blocking Po2 VLAN: 2,5,101,105,109.

06:55:48   %STP-2-VPC_PEER_LINK_INCONSIST_BLOCK: vPC peer-link detected Bridge Assurance Inconsistency blocking Po2 VLAN: 1-2,4-5,101,103,105,107,109.

06:55:54   %STP-2-BRIDGE_ASSURANCE_BLOCK: Bridge Assurance blocking port Po2 VLAN: 1-2,4-5,101,103,105,107,109.

06:56:22   %ETH_PORT_CHANNEL-5-PORT_DOWN: port-channel2: Ethernet2/14 is down

06:56:22   %ETH_PORT_CHANNEL-5-FOP_CHANGED: port-channel2: first operational port changed from Ethernet2/14 to Ethernet2/16

06:56:22   %ETHPORT-5-IF_DOWN_INITIALIZING: Interface Ethernet2/14 is down (Initializing)

06:56:32   %ETH_PORT_CHANNEL-4-PORT_INDIVIDUAL: port Ethernet2/14 is operationally individual

06:56:32   %ETHPORT-5-IF_UP: Interface Ethernet2/14 is up in mode trunk

06:56:33   %ETH_PORT_CHANNEL-5-PORT_DOWN: port-channel2: Ethernet2/16 is down

06:56:33   %ETH_PORT_CHANNEL-5-FOP_CHANGED: port-channel2: first operational port changed from Ethernet2/16 to Ethernet2/13

06:56:33   %ETHPORT-5-IF_DOWN_INITIALIZING: Interface Ethernet2/16 is down (Initializing)

06:56:33   %ETH_PORT_CHANNEL-5-PORT_DOWN: port-channel2: Ethernet2/15 is down

06:56:33   %ETHPORT-5-IF_DOWN_INITIALIZING: Interface Ethernet2/15 is down (Initializing)

06:56:36   %VPC-2-VPC_SUSP_ALL_VPC: Peer-link going down, suspending all vPCs on secondary

So basically, after this, all the links from the vPC unbundled. Has anyone come across this issue before?

Any thoughts would be highly appreciated.


Everyone's tags (7)
Cisco Employee

vPC Peer-link is down whereas vPC peer is alive

Looks like your L2 vPC environment is not configure correctly. Nothing much I can see here except I will not split up spanning-tree root between switches in vPC. They can all be in the same switch since vPC will always forward traffic.

If you post the config here, I can take a quick look to see if I can spot anything wrong with it.