Networking Tasks. Strange fall

    New network puzzle from unusual.

    Here is a simplified topology:

    We have a core network running MPLS TE. On top of the network, a VPLS service is organized for a large client.
    Between routers, TE tunnels are pulled into which VPLS traffic is wrapped using policies.

    What equipment is behind our routers, you can only guess, but we trust their QoS tags and we know that the main type of traffic comes with EF tags.

    One wonderful morning, everything disappeared - two links, depicted in red, fell (physically, torn optics, for example). And it would seem logical that nodes 2 and 3 became inaccessible. But here's the oddity: after them, the client began to complain about problems with node 4 - the services also stopped working. After repairing damaged lines, everything was repaired on all nodes.

    Attention, experts, the question is: who is to blame and what to do?

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