STP question forcing blocked port when forwarding port has BPDU filter enabled

[juan-ruiz]

Can I force a port to be in blocking state even if the forwarding port that connects to the layer 2 domain has BPDU filter enabled on it (STP off)?

The current layout:

Switch 1 connects on port g1/0/1 to the layer 2 domain and learns all MAC addresses and has stp off on it with the BPDU filter command applied to it.

Switch 2 connects on port g1/0/1 to the same layer 2 domain as switch 1 and learns all MAC addresses and has stp off on it with the BPDU filter command applied to it.

I now want to connect g1/0/2 on switch 1 and switch 2 to each other but I want to prevent the loop and force this link to be in blocked state.

I know I can increase the port priority and port cost  on g1/0/2 but will this configuration take affect if g1/0/1 does not participate in STP due to the BDPU filter applied?

[paul driver]

Hello

Remove the bpdu filter from both g1/0/1 ports of the two switches and then connect them together, this way the g1/0/1 ports of both switches should still be in a forwarding state as they will be both closest to the root switch and the ports gig1/0/2 interconnecting switch 1-2  should be where designated and blocking occur.

[juan-ruiz]

Hi Paul,

I'm going to consider this but I'm not sure if we can remove the BPDU filter.

Another thought I had was to enable flex link on the g1/0/1 and use g1/0/2 as the backup port.

Thank you for your reply!

[Reza Sharifi]

Hi,

STP being turned off is a dangers thing for your network.  If someone connects a cable to 2 different ports on a switch, it will cause a broadcast storm and bring down the whole network.  What Paul suggested should be considered. Also, not every platform and IOS supports flex link. It's an older technology that may not be supported by your IOS.

HTH