as far as I read only port up/downs can trigger TCNs.
I have got 4 switches connected to each other.
The direct link to the root bridge breaks down. The other switch (switch2) now asumes
itself as root. I guess that's the reason why it does not start to send a
tcn. But I don't understand why it does not receive a tcflagged bpdu from
the old root coming from the other path.
switch2 sets the topology change flag when it sends out its bpdus with its
own id as root id. As it receives a better bpdu (without tc-flag). It sends
Do you have an explaination why the TCN is sent 20 seconds after the port
went down? Afaik receiving a better Bpdu should't result in sending TCNs.
10x switch2-> switch1 ConfBPDU: (root=switch2)+TCFlag
1x switch1<- switch2 ConfBPDU: (root=switch3)
1x switch2 > switch1 TCN
Thank you very much for any tipps!!
best wishes from austria =)