spanning-tree inconsistent peer vlan error with RSPAN

[Dileep Sivadas Padmini]

Hi Everyone,

I am facing an issue with RSPAN configuration where source and RSPAN destination vlan get blocked due to spanning-tree Port VLAN ID Mismatch error on uplink switch.

Network diagram

    3750E (IOS 12.2-55)             3750 (IOS 12.2-55)
-----SW1---------------------------------------SW2-------
      |  gig1/0/24                  fa1/0/24
      |
      |

gig1/0/2 (RSPAN Destination port)

The configuration snippet on these switches

SW1 (where RSPAN destination port configured)
===========================

vtp mode transparent
vlan 300
name data
vlan 400
name voice
vlan 800
remote vlan

spanning-tree mode rpvst

spanning-tree vlan 1,300,400,800 root primary

monitor session 1 destination interface gig1/0/2
monitor session 1 source remote vlan 800

interface gig1/0/24
switchport trunk encapsulation dot1q
switchport mode trunk

SW2
====
vtp mode transparent
vlan 300
name data
vlan 400
name voice
vlan 800
remote vlan

spanning-tree mode rpvst

monitor session 1 source vlan 400 rx
monitor session 1 destination remote vlan 800

interface fa1/0/24
switchport trunk encapsulation dot1q
switchport mode trunk

Under above configuration VLANs 400 and 800 are blocked due to spanning-tree "Port VLAN ID Mismatch error"

I also notice that error went away  if I make any of the following configuration changes.

1. If I disabled RSPAN configuration on SW2.

2. If I configure ISL encapsulation instead of dot1q

Any help to resolve this issue with dot1q encapsulation is greatly appreciated.

Thanks

Dileep

[Dileep Sivadas Padmini]

Has anyone faced this issue?

After enabling RSPAN on sw2 with dot1q encapsulation I am getting following logs.

%SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 400 on GigabitEthernet1/0/24 VLAN800.
%SPANTREE-2-BLOCK_PVID_PEER: Blocking GigabitEthernet1/0/24 on VLAN0400. Inconsistent peer vlan.
%SPANTREE-2-BLOCK_PVID_LOCAL: Blocking GigabitEthernet1/0/24 on VLAN0800. Inconsistent local vlan.

sw1#show spanning-tree inconsistentports

Name                 Interface                Inconsistency
-------------------- ------------------------ ------------------
VLAN0400             GigabitEthernet1/0/24    Port VLAN ID Mismatch
VLAN0800             GigabitEthernet1/0/24    Port VLAN ID Mismatch

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

sw1#

sw1#show spanning-tree vlan 400

VLAN0400
  Spanning tree enabled protocol rstp
  Root ID    Priority    400
             Address     d0d0.fd27.1d00
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    400    (priority 0 sys-id-ext 400)
             Address     d0d0.fd27.1d00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/0/1             Desg FWD 4         128.1    P2p
Gi1/0/24            Desg BKN*19        128.24   P2p *PVID_Inc

sw1#show spanning-tree vlan 800

VLAN0800
  Spanning tree enabled protocol rstp
  Root ID    Priority    800
             Address     d0d0.fd27.1d00
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    800    (priority 0 sys-id-ext 800)
             Address     d0d0.fd27.1d00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/0/1             Desg FWD 4         128.1    P2p
Gi1/0/24            Desg BKN*19        128.24   P2p *PVID_Inc

sw1#

Thanks

Dileep

[ranraju · Accepted solution]

Hi Dileep

Most likely you are hitting this bug CSCtj76880 here on the 3750 switch... this is seen version 12.2(55)SE... and a fix to this would be available in the versio 12.2(58)SE...

And all of them indicates that you are hitting this bug... when you say it works with the following configuration changes...

1. you disable RSPAN session.

2. when you use ISL instead of dot1q

3. making the switch2 as root where you have configured the RSPAN....

Hope this helps..

(please rate helpful posts)

Regards,

ranraju

[Dileep Sivadas Padmini]

Hi Ranraju,

Thanks for the information.

Regards

Dileep

[ranraju]

just to add on to the above....

Here the switch2 has RSPAN configured. So the RSPAN is making a copy of the BPDUs for vlan 400 --- which will now be in vlan800.. (which should not happen, this is not how it should work and not an expected behavior), so since you are allowing this vlan on the trunk, the switch1 is receiving BPDU of vlan400 on vlan800. Seeing this inconistency, the switch1 puts the port in BLK state for vlan400 and vlan800. If you want to read more about PVID inconsistency you refer to the following link: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00801d11a0.shtml

Hope this answers you questions on this post...

(please rate helpful posts..)

Regards,

ranraju