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Spanning Tree and PVID Issue

jonhill
Level 1
Level 1

I've just had a switch stach mysteriously drop off the network, when I did a reload to see if that would solve it the console showed the following errors.

SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 1 on GigabitEthernet0/1 VLAN2.

000059: Apr 22 14:52:51: %SPANTREE-2-BLOCK_PVID_PEER: Blocking GigabitEthernet0/1 on VLAN0001. Inconsistent peer vlan.

000060: Apr 22 14:52:51: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking GigabitEthernet0/1 on VLAN0002. Inconsistent local vlan

VLAN 2 is configured on the switch but is not currently used by any ports, if I remove VLAN 2 Spanning-tree unblocks the ports and everything works again.

What I don't understand is that this VLAN has been configured on this switch since it was installed about 6 weeks ago and other Cisco switches on-site configured with VLAN 2 have not shown the same problem.

Our currant setup is a 3COM 4060XRN in the core with Cisco 2950's on the edge.

This is the first issue we've had with this problem, are we likely to see others, is it a problem between the 3COM and Cisco switches?

Thanks

Jon

9 Replies 9

milan.kulik
Level 10
Level 10

Hi,

it seems like some kind of vendor incompatibility.

How is the trunk configured on the Cisco and 3Com side?

Which VLAN is the native one on Cisco and 3Com?

Ar eyou running PVSTP+ on the Cisco switch?

See also BPDU Formats part in http://www.cisco.com/warp/customer/473/103.html#stp for details.

Regards,

Milan

The 3COM end is on it's default settings and the Cisco is setup using the smartport macros.

Both Cisco and 3COM switches are using VLAN 1 as the default VLAN.

I noticed from the config on the switch that VTP is setup in server mode would it be worth putting it in transparent mode so it does not broadcast VLAN info, could this of been causing the problem?

Yes we are using PVST+ on the Cisco.

Thanks

Hi,

I don't think this is a VTP problem.

It seems like native VLAN problem.

The TAC Error Decoder tool says:

1. %SPANTREE-2-RECV-PVID-ERR: Received BPDU with inconsistent peer vlan id [dec] on [chars] [chars].

This message means that the listed interface received an SSTP BPDU that is tagged with a VLAN ID that does not match the VLAN ID on which the BPDU was received. This occurs when the native VLAN is not consistently configured on both ends of an 802.1Q trunk. [dec] is the VLAN ID, the first [chars] is the port, and the second [chars] is the VLAN.

Recommended Action: Verify that the configurations of the native VLAN ID are consistent on the interfaces on each end of the 802.1Q trunk connection. When the configurations are consistent, spanning tree automatically unblocks the interfaces.

Related documents- No specific documents apply to this error message.

AFAIK, 3Com switches have no native VLAN configured by default, so I'd check the 3Com config for the native VLAN.

Regards,

Milan

All the ports on our 3COM switches are associated with VLAN 1.

I've checked both ends and as far as I can make out they are configured correctly. All our other switches are configured the same as the one that is giving us hassel.

I have managed to rectify the problem by deleting VLAN 2 from the Cisco switch at which point the uplink came up and worked.

What I would like to know is what the easiest way of finding out if it's a compatability issue between 3COM and Cisco, they will blame each other and we will get nowhere fast.

Thanks

Hi,

it might be another trunk misconfigured.

See http://www.cisco.com/en/US/customer/tech/tk389/tk621/technologies_tech_note09186a00801d11a0.shtml

(or http://www.cisco.com/warp/public/473/pvid_inconsistency_24063.pdf for .pdf version)

for explanation.

I'd try STP debug to see what's exactly coming to your Cisco switch from the 3Com.

Regards,

Milan

I've just heard back from 3COM and the 3COM kit does not support PVST so I need to disable PVST on the Cisco 's. How do I go about turning of PVST and just running RSTP?

Hopefully this may solve the issues we are experiencing.

Thanks for your help.

Hi,

does it mean you're running Rapid Per-VLAN STP on your Cisco 2950 connected to a 3Com switch which is connected to a core running Rapid Per-VLAN STP again?

If yes, you can get into a seious trouble, depending on your topology, I'm afraid.

RPVSTP is backward compatible to PVSTP, but including MonoSTP 3Com switch in the network can make it much more complicated, I'm afraid.

Regards,

Milan

Regards,

Milan

The way the network is configured is a 3COM core running RSTP and our edge switches CAT2950 running PVST+ will the PVST+ cause issues with STP on the 3COM core?

Thanks

It's possible.

I've got no knowlege how RSTP is implemeted on 3Com switches.

Regards,

Milan

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