[j-nsp] Topology failure on EX4200

Victor Sudakov vas at mpeks.tomsk.su
Mon Jul 10 23:59:58 EDT 2017

One more observation: OSPF adjacency in the management vlan does
not break, so I conclude that only unicast traffic is affected.

Victor Sudakov wrote:
> There is a ring of EX4200 switches, please look at http://noc.sibptus.ru/jun1.png
> If MUX1 fails, the MSTP topology adjusts and the PCs continue to see
> one another just fine.
> However, some switches become inaccessible in the management vlan
> (vlan3 in this example). For example, you can still ping
> from, but not from
> One important note. If MUX1 fails, the corresponding interfaces on
> and don't go down, it is only the traffic
> (including BPDUs) that stops flowing through the mux.
> If I shutdown the corresponding interfaces on and
> (or use OAM to shutdown the interfaces automatically when
> the mux fails), the problem disappears and I can ping any switch from
> any switch.
> What's the theory behind this?
> "clear arp" and "clear ethernet-switching table" don't fix the
> problem.
> -- 
> Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
> AS43859
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Victor Sudakov,  VAS4-RIPE, VAS47-RIPN

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