STP BPDU filter / guard - a little bit inefficient?

Hello all,

My problem is not directly related to CCIE exam, but rather to CCIE topics. I have an issue and I don't know what solution to propose, so maybe you can help me a little bit.

1. Let's assume that we have a L2 switch, with one or two uplinks, with BPDU guard / filter enable and also portfast. Everything is running fine.

2. Somebody come and connected to one of the edge ports of L2 a hub. L2 switch will start to send BPDUs, but since at the other end there is no switch, but a hub, it will get nothing back (in terms of BPDU packets) and assume that an end device (e.g. PC) is connected there. Still, everything is running fine.

3. Another (smart) somebody come and plug a loop in the hub (one cable; both ends in the same hub). Since the port is already UP on the L2 port, no BPDU flow through there, the BDPU guard / filter will not react, but the hub will loop all other packets and send them to L2 switch. From this point a little bit of disaster in the spanning-tree environment.

I have no idea how to stop this issue from happening, beside adding there a sign on L2 switch with "you plug something here and you die" or enabling port-security (which let's say I don't want for certain personal reasons).

Please let me know if I miss something in my problem (from logical point of view) and if you have any possible solution to my problem.

Thanks for your time!

Cheers,
Calin

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Received on Wed Aug 31 2011 - 08:45:43 ART