[c-nsp] N9K traffic lost when redundant link comes up

Lukas Tribus lukas at ltri.eu
Tue Mar 9 13:40:00 EST 2021

On Tue, 9 Mar 2021 at 18:08, <cnsp at marenda.net> wrote:
> Expected behaviour is:
> New link gets active, and
> if spanning tree finds this new link as "lower" it would block it.
> if spanning tree finds it "better" it should start to use it and block somewhere else.
> But monitoring was crying, and I found in the loggin:
> 16:30:19 dsw2 %L2FM-2-L2FM_MAC_FLAP_DISABLE_LEARN: Disabling learning in vlan XXX for 120s due to too many mac moves
> 16:32:19 dsw2 %L2FM-2-L2FM_MAC_FLAP_RE_ENABLE_LEARN: Re-enabling learning in vlan XXX
> Yes, that was also the duration of the "outage", adding a redundant link leads two two minutes outage ☹
> Cisco's error-messages finder tells me that there is nothing to do  ?!?
> Case opened, infos submitted, but two days (plus weekend) silence.
> Any idea what is happening and how I can avoid that (the fourth link wants to be plugged in).

It fires because of too many mac moves, so increase logging level to
see every single mac move and then find out why that is.


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