PVID_Inconsistency for one Cisco3750 switch, not for the other.

[--JayJay--]

In a trunked topology with an (HP)ArubaOS-switch together with two C3750 switches connected in a triangle and a mismatched native VLAN setup between the ArubaOS (untagged 10) on one hand and the Cisco's on the other hand (ntaive 1).

One of the Cisco switches is blocking port towards the ArubaSwitch due to PVID_Inc (Port VLAN ID Incosistency)  as displayed in the output of command "show spanning-tree".

The other Cisco switch does not have this issue with the ArubaSwitch, while the setting on the ArubaSwitch is the same for both trunks towards the Cisco equipment/switches.

The command "vlan dot1q tag native" has NOT been configured on the Cisco3750 switches.

I do not want to discuss the native VLAN mismatch and the reason for this architecture. 
I 'ld like to know why one of the Cisco 3750 switches is working fine in this configuration , while the other one blocks it's port due to PVID_Inc.

Can it be that either the software version or the license is playing a part in the issue?

Cisco switch without the issue:

Hardware WS-C3750X-24 (PowerPC405)
Image C3750E-UNIVERSALK9-M
IOS Version 12.2(55)SE10

Cisco switch blocking port due to PVID_Inc:
hardware WS-C3750G-24TS-1U (PowerPC405)
Image Version IOS C3750-IPBASE-M

IOS version 12.2(25r)SE1

[Reza Sharifi]

The license usually does not play a part for this type of issues.

It could be a bug in the IOS you are running.  Can the WS-C3750G-24TS-1U be upgraded to 12.2(55)SE10?

HTH

[Matt Delony]

Hello --JayJay--,

PVID inconsistency occurs when PVST BPDU is received on different VLAN than what's listed in the originating VLAN field in the incoming BPDU. Usually this occurs with a native VLAN mismatch.

I don't believe license level and IOS version should be contributing to this issue.

It's hard to say what's going on without seeing any outputs. But I would examine the following outputs from the 3750's to start with to get an idea of what's going on:

• show spanning-tree vlan 1
• show spanning-tree vlan 1 detail
• show spanning-tree vlan 10
• show spanning-tree vlan 10 detail
• show spanning-tree inconsistentports
• show interface x/y trunk
• show interface x/y switchport

[paul driver]

Hello

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@--JayJay-- wrote:

In a trunked topology with an (HP)ArubaOS-switch together with two C3750 switches connected in a triangle and a mismatched native VLAN setup between the ArubaOS (untagged 10) on one hand and the Cisco's on the other hand (ntaive 1).

One of the Cisco switches is blocking port towards the ArubaSwitch due to PVID_Inc (Port VLAN ID Incosistency)  as displayed in the output of command "show spanning-tree".

The other Cisco switch does not have this issue with the ArubaSwitch, while the setting on the ArubaSwitch is the same for both trunks towards the Cisco equipment/switches.

I 'ld like to know why one of the Cisco 3750 switches is working fine in this configuration , while the other one blocks it's port due to PVID_Inc.

---

Just confirm you asking for a reason why when two sides of a trunk has a configuration native vlan mismatch the misbehaving bpdu port goes into a pvid inconsistent state - correct?

[--JayJay--]

With the setup as pictured in the attachment.
Why is one of the C3750-switches going into PVID_Inc state and the other one not.

Meanwhile in a Lab setup I 'm able to reproduce the issue with different equipment.

Being a single HP-Aruba-2530  connected on a dot1Q trunk to a  single Cisco-3550 (12.2(52)SE) .

Native VLAN 10 on the HP-Aruba, on the Cisco native VLAN 1.

With the HP-Aruba set to spanning tree mode Rapid-PVST and the Cisco 3550 to Rapid-PVST as well, the PVID_Inc state is triggered.

When changing the STP mode on the Cisco 3550 to PVST the issue resolves.

[paul driver]

Hello

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@--JayJay-- wrote:

With the HP-Aruba set to spanning tree mode Rapid-PVST and the Cisco 3550 to Rapid-PVST as well, the PVID_Inc state is triggered.

When changing the STP mode on the Cisco 3550 to PVST the issue resolves.

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I cannot answer for the HP Aruba switch but it may be its possible that HP device isn't PVST vlan aware as such doesn't see the inconstancy, so its then like tagging the native vlan and such no PVID_Inc?