Hi, I am seeing this messages across my network as per attach picture. Should I be worried of this topology changes stp.flags.tc==1 . I also saw there is no stop.flags.tack==0 Or perhaps something misconfiguration on the STP? Thanks. asked 25 Jul '14, 20:50  Macha |
One Answer:
To confirm whether it's a problem, trace it to the source switch and check the status of its interfaces. It could be a flapping Ethernet link to something unimportant, or it could be a critical trunk (the trace won't tell you that). TCN BPDUs don't rigger any kind of network recalculation, so the packet itself shouldn't really cause harm. All it does is speed up the age out timer for related mac addresses. Also note, the TCN BPDU is sent out on root ports and should be acked by the immediate switch upstream. Perhaps your trace isn't capturing both sides of the connection? It is odd for them to not be acknowledged. answered 25 Jul '14, 21:50  Quadratic |
Hi,
Thanks for the reply. Indeed, this capture only from one side.
regards.
Just follow the BPDU to the originating switch. My guess is it's simply a physical interface flapping. Depending on how you have this set up, it could even be the link between an access switch and one client workstation.