Hi everybody,

we have an installation made of a loop with 25 RB260GS, each of them connected to another with a copper patch ( 1mt ) on a side and with a fiber link using gigabit SFP ( 30 to 100 mt ) on the other side.
we have 3 vlan on this loop, enabled in every RB260, and we enabled Independent VLAN Lookup everywhere.

so far so good.

sometimes this loop starts having problem with spanning tree, having some RB260 that become unreachable for 3-5 sec. every 10 sec. with root port that change with no sense in those switches.

during one of these situations, we tried to open the loop, in order to stop spanning tree strange behaviour, and we found out that the switch on the other side of the disabled fiber link, that should see the link down, keep selecting fiber port as root port, as he receive spanning tree valid packet on the disabled link!

and we learned that to exit from these situations, we have to reboot that single switch that has decided to keep seeing spanning tree packet from port. previously we just switched off and on all of them to recovery from these situations.

we replaced SFP and RB260 that was found having this strange behaviour, and we recheckd fiber links, but nothing really changed, after from 2 to 6 week the problem came back. we suspect that starts when one or a partial group of RB260 has little power outages.

we are currently using swos 2.13

have you got any suggestion?

thanks