Summary
Add the "log-session-changes" option for BFD protocol which is available in FRR and also the other protocols like ospf and bgp have in VyOS CLI.
vyos(config-bfd)# peer 192.168.0.1 vyos(config-bfd-peer)# detect-multiplier Configure peer detection multiplier echo Configure peer echo intervals echo-interval Configure peer echo intervals echo-mode Configure echo mode end End current mode and change to enable mode exit Exit current mode and down to previous mode find Find CLI command matching a regular expression list Print command list log-session-changes Log Up/Down changes for the session vyos@vyos# set proto bfd peer 1.1.1.1 Possible completions: echo-mode Enables the echo transmission mode > interval Configure timer intervals minimum-ttl Expect packets with at least this TTL multihop Allow this BFD peer to not be directly connected passive Do not attempt to start sessions profile Use settings from BFD profile shutdown Disable this peer > source Bind listener to specified interface/address, mandatory for IPv6 vrf VRF instance name
Use case
Enables or disables logging of session state transitions into Up state or when the session transitions from Up state to Down state.