link monitoring

Thu Apr 29 20:39:16 UTC 2021

Hello

We had a 100G link that started to misbehave and caused the customers to
notice bad packet loss. The optical values are just fine but we had packet
loss and latency. Interface shows FEC errors on one end and carrier
transitions on the other end. But otherwise the link would stay up and our
monitor system completely failed to warn about the failure. Had to find the
bad link by traceroute (mtr) and observe where packet loss started.

The link was between a Juniper MX204 and Juniper ACX5448. Link length 2
meters using 2 km single mode SFP modules.

What is the best practice to monitor links to avoid this scenarium? What
options do we have to do link monitoring? I am investigating BFD but I am
unsure if that would have helped the situation.

Thanks,

Baldur
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