Cisco SD-WAN BFD State INIT

[RS19]

I have Cisco ASR1001 SD-WAN device. Recently there was flap observed in BFD sessions . Most of the BFD sessions were up but 2 BFD sessions are down
When I used the command show platform hardware qfp active feature bfd datapath sdwan summary & I am getting that the state is INIT

Wanted to understand what is the reason for this INIT & how should I identify and troubleshoot it.
Pls help.

[RS19]

Not able to attach the screen shot due to some reasons.

But the state says that it is in INIT stage

[bigevilbeard]

Take a look at this TS doc which was uploaded by a memeber of the community - https://community.cisco.com/kxiwq67737/attachments/kxiwq67737/4461-docs-network-infrastructure/5812/1/SDWAN%20BFD%20Troubleshooting.docx

INIT is the starting state where the BFD session first tries to establish communication before it can verify connectivity and become operational. A session stuck in INIT points to a problem in this initial negotiation process that needs to be investigated and rectified.

[RS19]

I have gone through the docu, but sitll could not able to figure what is causing this issue ?

Any help or inputs will be helpful.

[RS19]

Also wanted to understand what are the reasons the state is in INIT stage ?

What could be the scenarios ?

[svemulap@cisco.com]

INIT state is a state means that {RFC 5880}


the remote system is communicating, and the
local system desires to bring the session up, but the remote system
does not yet realize it. A session will remain in Init state until
either a BFD Control Packet is received that is signaling Init or Up
state (in which case the session advances to Up state) or the
Detection Time expires, meaning that communication with the remote
system has been lost (in which case the session advances to Down
state).

[svemulap@cisco.com]

Also go through -

https://www.cisco.com/c/en/us/support/docs/routers/sd-wan/214510-troubleshoot-bidirectional-forwarding-de.html

https://www.cisco.com/c/en/us/support/docs/routers/vedge-router/215359-bidirectional-forwarding-detection-flap.html#

[RS19]

Thanks. I checked the link. But still not able to sort it out.

When I typed the command show sdwan omp tlocs , the bfd status of that particular link is showing down.

[svemulap@cisco.com]

Based on what you describe, you seem to have an underlay (reachability) problem (between the sites)
w/o topology diagram and show/debug commands, it is difficult to help here.

Please open a TAC Case, so your issue can be addressed.

[RS19]

thanks I do understand your point that it requires logs & the diagram.

Would like to understand that in case there is underlay problem how come some of the bfd sessions using the same underlay is working & only 3 bsd sessions are not working. 

I think there is flap in the underlay network, because of that all the BFD sessions went down. Most of the BFD sessions came up, but only 3 bfd sessions didnt come up.

What could be the reasons ? Theoritical reason also I am ok for now as explanation  ?

[RS19]

After troubleshooting & analyzing it was identified that the issue is due to the transport layer (Metro Ethernet)
One of the interface (Metro Ethernet Interface) Gi0/4 needs to be disabled & enabled to fix it.

Any Idea how to do it ?  Has this to be done via CLI or via Templates ?

The SD-WAN model is ASR1001-X 

[Torbjørn]

The easiest way to do this would be to "shut" then "no shut" the interface from the CLI.