stp guard loop

[suthomas1]

Hello All,

We were trying to add a vlan on one of the downstream access switches when we found that it wasn't showing the correct root for this vlan.

Logs show the below message:-

NW-TDC-N95-2 %STP-2-LOOPGUARD_BLOCK: Loop guard blocking port port-channel12 on VLAN2115. configuration for po12 is:-

interface port-channel12
  description vPC Link to NW-TDC-N9372
  switchport mode trunk
  spanning-tree guard loop
  mtu 9216
  storm-control broadcast level 10.00
  storm-control multicast level 10.00
  vpc 12

sh vpc 12

vPC status
----------------------------------------------------------------------
id   Port   Status Consistency Reason                     Active vlans
--   ----   ------ ----------- ------                     ------------
12   Po12   up     success     success   

Rest of all the vlans on this switch appear fine with correct root..this is the only one giving this problem.

Appreciate all help. thanks in advance.

[InayathUlla Sharieff]

Which device is STP ROOT for thise vlans ?  the device reporting this error or some other device ?

Do you have vPC feature enabled ? If so, do you have "peer-switch" enabled on vPC peers ?

[suthomas1]

The device showing this error is the core switch(NW-TDC-N95-2) for this particular physical DC.

there is another DC( which usually has the main stp roots for all vlans in network) which is connected over layer 2 links to this particular DC.

interface port-channel12
  description vPC Link to NW-TDC-N9372 >>>this interface on NW-TDC-N95-2 links to distribution switch NW-TDC-N9372.

How do we check the "peer-switch" enabled on vpc peers? is there any command i can use.

vpc feature is enabled on these devices.

thank you.

[InayathUlla Sharieff]

You can use the command:- 

Command: show running-config vpc
 

version 6.2(10)
feature vpc

vpc domain 500
  peer-switch>>>>>> here you can see.

Some info on the same:-

https://supportforums.cisco.com/document/118156/nexus-peer-switch-feature-hybrid-setup

HTH