[j-nsp] Topology failure on EX4200

[Roger Wiklund]

Hi

Have you configured loop protection?
https://www.juniper.net/documentation/en_US/junos/topics/example/stp-loop-protection-qfx-series.html

On a design note, why not use Virtual Chassis instead?

/Roger

On Mon, Jul 10, 2017 at 6:34 AM, Victor Sudakov <vas at mpeks.tomsk.su> wrote:
> Dear Colleagues,
>
> 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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