When one of the channels goes down and in order not to wait for a timer of tens of seconds to break the BGP session and delete the routes, it was necessary to configure the BFD (Bidirectional Forwarding Detection) protocol, which allows you to immediately notify BGP about this and delete the routes going through the non-working neighbor.
Let’s say I have BGP configured on MX204 in groups, each group has several neighbors of the same AS, all neighbors already have BFD configured, then we will configure BFD for the group:
edit protocols bgp group IXNFO.COM
set bfd-liveness-detection minimum-interval 300
set bfd-liveness-detection multiplier 12
Or you can configure this group only for a specific neighbor:
set neighbor 10.10.55.55 bfd-liveness-detection minimum-interval 300
set neighbor 10.10.55.55 bfd-liveness-detection multiplier 12
You can temporarily configure tracing so that more information about BDF is written to the logs:
set protocols bfd traceoptions file bfd-trace
set protocols bfd traceoptions flag all
file show /var/log/bfd-trace
show interfaces
show protocols
show routing-options
Let’s save the configuration:
commit check
commit comment "BFD"
Let’s look at the information about the sessions:
show bfd session extensive
See my other articles about Juniper