BFD isn’t working with IPv6 and routing protocols that use their loop back addresses for negotiation. When the BFD control packet is sent the src-address is using the IPv6 address of the physical exit interface instead of the loop-back that was configured.
Loop-backs:
2620:d8:e000:FFFF::1 on the CCR2116.
2620:d8:e000:FFFF::2 on the SXT LTE 6.
Src used:
fd3d:c865:2fc0:2:: on the CCR2116
fd3d:c865:2fc0:2::1 on the SXT LTE 6
The addresses show properly on the BFD session
[TrevinLC1997@SXT_LTE6] > /routing/bfd session print
Flags: U - up, I - inactive
0 multihop=yes vrf=main remote-address=2620:d8:e000:ffff::1 local-address=2620:d8:e000:ffff::2 state=down state-changes=0
desired-tx-interval=1s actual-tx-interval=1s required-min-rx=1s remote-min-rx=1us multiplier=5 packets-rx=0 packets-tx=10
I've noticed a work around is using src-nat and changing the src-address to the correct loopback. After you do that the BFD session will come up successfully.
Figured I'd post just in case someone else has experienced this issue. I do have it reported. SUP-195726