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New Member

Native VLAN mismatch issue on Cat 3750 with Intrushield

I am trying to partition off 4 sections of the Cat 3750, to act as virtual switches separate from each other. I want traffic to go from VLAN 2, through an Intrushield device, to VLAN 3 which has the gateway port. Whenever I connect the Intrushield, I get Native VLAN mismatch messages on the switch console and the communication does not work. I understand that the switch is seeing the same traffic on 2 different VLANs (exiting out a port on VLAN 2, traversing the Intrushield, and re-entering the switch on VLAN 3)and is complaining. Does anyone know how to do this? Do I need to buy separate switches, or can the cat 3750 be partitioned this way? If it can, how?


Re: Native VLAN mismatch issue on Cat 3750 with Intrushield


assuming that the Intrushield is basically transparent and just monitoring the frames, I would assume the BPDUs will trigger those messages. In principle you could get the same result when connecting the VLAN2 port and the VLAN3 port with a crossover cable.

You could setup BPDU filter on the respective ports to block BPDUs.

Can you please check in "Understanding BPDU Filtering"

whether this resolves your issue.

Hope this helps! Please use the rating system.

Regards, Martin

New Member

Re: Native VLAN mismatch issue on Cat 3750 with Intrushield

This was very helpful. I turned on BPDU filtering, but I was still getting the messages on the console. I then disabled CDP on those same interfaces and the messages went away. Everything is working as I envisioned it originally.


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