Nexus vPC and spanning tree

[mohammedrafiq]

Hi,

I have configured my 4Nexus switches as diagram shown (see attachment).All the vPC between 7018 and 5548 is working fine.Now I have created VLAN 99 on all four switches But spanning tree keep blocking vlan 99 on both 7018 switchsand I am loosing connectivity.My undestanding is if vPC working fine, there should not be any blocking ports.

NIAC-7018-1# sh vpc
Legend:
                (*) - local vPC is down, forwarding via vPC peer-link

vPC domain id                   : 1
Peer status                     : peer adjacency formed ok
vPC keep-alive status           : peer is alive
Configuration consistency status: success
Type-2 consistency status       : success
vPC role                        : primary
Number of vPCs configured       : 2
Peer Gateway                    : Disabled
Dual-active excluded VLANs      : -

vPC Peer-link status
---------------------------------------------------------------------
id   Port   Status Active vlans
--   ----   ------ --------------------------------------------------
1    Po1    up     1,99

vPC status
----------------------------------------------------------------------
id   Port   Status Consistency Reason                     Active vlans
--   ----   ------ ----------- ------                     ------------
3    Po3    up     success     success                    1,99

4    Po4    up     success     success                    1,99
----------------------

NIAC-7018-1# sh spanning-tree blockedports

Name                 Blocked Interfaces List
-------------------- ------------------------------------
VLAN0001             Po3
VLAN0099             Po3

Number of blocked ports (segments) in the system : 2

[Amit Singh]

Mohammed,

What does the " show spanning-tree bloacked ports" list you? Could you please paste that. From the spanning-tree perspective it would ideally block one side. STP is used a fail-over mechanism if the VPC algorith fails. If STP is blocking the same vlans on both the links, then there is some problem with the configuration.

Please use the deisgn guide below for a VPC design.

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/C07-572829-01_Design_N5K_N2K_vPC_DG.pdf

HTH,

-amit singh's

[Amit Singh]

Hi Mohammed,

I requested the output from 2nd 7018. Forgot to mention that.

Cheers,

-amit singh

[mohammedrafiq]

Hi Amit,

Please see output from second 7018.Interface Vlan 99 is not blocked on Po4, VLAN 99 is blocked on both switches in PO3

it might be normal behaviour for spanning tree under vPC , I am just want to confirming it.

NIAC-7018-2# sh spanning-tree blockedports

Name                 Blocked Interfaces List
-------------------- ------------------------------------
VLAN0001             Po3
VLAN0099             Po3

Number of blocked ports (segments) in the system : 2

NIAC-7018-2# sh vpc
Legend:
                (*) - local vPC is down, forwarding via vPC peer-link

vPC domain id                   : 1
Peer status                     : peer adjacency formed ok
vPC keep-alive status           : peer is alive
Configuration consistency status: success
Type-2 consistency status       : success
vPC role                        : secondary
Number of vPCs configured       : 2
Peer Gateway                    : Disabled
Dual-active excluded VLANs      : -

vPC Peer-link status
---------------------------------------------------------------------
id   Port   Status Active vlans
--   ----   ------ --------------------------------------------------
1    Po1    up     1,99

vPC status
----------------------------------------------------------------------
id   Port   Status Consistency Reason                     Active vlans
--   ----   ------ ----------- ------                     ------------
3    Po3    up     success     success                    1,99

4    Po4    up     success     success                    1,99

NIAC-7018-2#