BFD on ASR9K Cluster

[bjberginz]

I attempted to setup BFD on a layer3 subint on an ethernet bundle on an ASR9K cluster with two members.  The other end of the link is a ME3600X.  The BFD session did not come up, the status on the ASR side was 'ADMIN DOWN', I also saw log messages of this type:

%L2-BFD-6-SESSION_NO_RESOURCES

As well as:

show bfd session detail | inc “^(Location|MP)”
Mon Apr 28 06:51:23.228 UTC
MP download state: BFD_MP_DOWNLOAD_NO_LC

So there apparently wasn't a LC resource configured or available.  I did find a 'multipath include location' bfd command, I configured both LCs for it and the BFD session came up.  What's odd to me is that the only discussion that  can see of 'multipath' is in the context of multihop BFD sessions, which this one is not, the link does pass through an intermeidat l2 swtich, but the connection is a direct l3 link from ASR to 3600.  Why do I need the multipath command?

[xthuijs]

hi there, yeah when you have bundle and you are apparently running XR43 or later then you require the multipath location to tie the BFD session to a resource location.

This I think is maybe nicely explained with this: Implementation of various BFD flavours over bundle interfaces in IOS XR was carried out in 3 phases:

1. IPv4 BFD session over individual bundle sub-interfaces. This feature was called “BFD over VLAN over bundle”.
2. IOS XR releases 4.0.1 and beyond: “BFD Over Bundle (BoB)” feature was introduced.
3. IOS XR releases 4.3.0 and beyond: full support for IPv4 and IPv6 BFD sessions over bundle interfaces and sub-interfaces. For disambiguation from the BoB feature, this implementation is called BLB, and sessions are often referred to as native BFD sessions over bundle interfaces and/or sub-interfaces. BFD multipath must be enabled for any of these BFD flavours to work.

Due to the introduction of BLB (bfd over logical bundle) in XR43 this was necessary, I agree that you may have been mislead by the nomenclature of that multipath location keyword which suggests multihop, but it was meant to also include multipath as in multiple members of a bundle...

regards

xander

[jkhodabaksh]

worked for me too. 

however i was on an NCS540 platform 

thanks

[jcavallero]

This worked for me too!

But in my case I was trying to run BFD multihop (not multipath) for iBGP on a XRv 9000.

Regards,

Juan