Customer upgraded sbfd responder device. Replaced RE with new version and loaded saved configuration.

After that, customer found all sbfd sesstion to this responder are down.

user@mx> show spring-traffic-engineering lsp
To       State   LSPname
10.0.0.2    Down   SPRING-TE-LSP

From fpc shell commmand, there is no sbfd session.

SMPC0(mx vty)# show ppm adjacencies protocol bfd
<<<< no sbfd session>>>>

This issue can be reproduced follow below steps:

1.Delete all configuration, make sure there is "no lo0 configuration".

2.Configure lo0.100 and local-discriminator and then commit.

user@mx# set interfaces lo0 unit 100 family inet address 10.0.0.1/32 primary
user@mx# set protocols bfd sbfd local-discriminator 20000001

Not having lo0.0 configuration for sbfd is not acceptable as sbfd responder run in distributed/inline mode, for bfd distribution configuring lo0.0 is must.

Refer below reference:

https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/topic-map/bfd.html#:~:text=CPU%20is%20congested.-,Distributed%20Configuration%20and%20Support,0%20and%20the%20appropriate%20family.&text=This%20is%20true%20for%20the,%2C%20and%20VPLS)%20(MPLS)

“For distributed BFD to work, you need to configure the lo0 interface with unit 0 and the appropriate family.”

Restart ppmd can recover this error status.

> restart ppmd immediately

Adding lo0.0 configuration can avoid this issue.