[j-nsp] Topology failure on EX4200

[Victor Sudakov]

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 192.168.1.3
> from 192.168.1.2, but not 192.168.1.4 from 192.168.1.2.
> 
> One important note. If MUX1 fails, the corresponding interfaces on
> 192.168.1.2 and 192.168.1.4 don't go down, it is only the traffic
> (including BPDUs) that stops flowing through the mux.
> 
> If I shutdown the corresponding interfaces on 192.168.1.2 and
> 192.168.1.4 (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
AS43859