MSTP & RSTP Convergence Issues (ready to award points :))

[Jason Scott]

Hi all,

Our current network is mostly comprised of 9300s in the core and 5300/2600 switches in the edge. We have just added one 3500 switch which is running MSTP. This switch is connected to a 2600 and a 5300 with one of the links blocking accordingly.

However we have some servers connected via multiple NICs into the 3500 but these are having issues causing the links to repeatedly change status between up/down. When this occurs on the 3500 it is causing reconvergences across the whole network. We do not see this behaviour on the 2600s.

I've been reading up on MSTP and the switch is configured with the default settings/timers. CST isn't showing updates for the root bridge. Should I manually assign the server ports to admin-edge-port?

Thanks,

[Case Van Horsen]

I'm using 5400 and 3500 switches and I don't see that issue but I have all edge ports set to admin-edge-port. IIRC, in addition to forcing the ports into forwarding state immediately, it also stops topology change notice packets from originating from those ports.

casevh

[Jason Scott]

Thanks. I've forced the ports to admin-edge-port and its slowed the reconvergences but not stopped them completely.

[Matt Hobbs · Accepted solution]

How recent is your firmware on the 3500, I'd recommend updating to at least K.12.57 which includes the auto-edge-port feature (enabled by default) and a few other fixes to STP.

[Jason Scott]

We're on K.12.16. I'll give that a go and let you know how things are.

Cheers,

[Jason Scott]

That seems to have settled things down. the ports are still flapping (issue with the server) but spanning tree is not reconverging every minute.

Thanks.