CSCvs57057 - 9.3.3 "BFD is not supported on unnumbered interface"

[JasperHorng9198]

According to Cisco TAC, bfd on ip unnumbered interfaces is not supported. This was referenced in my ticket, SR 688160521.

This is unfortunate as we are running VxLAN with an ISIS ip unnumbered underlay with BGP on top. BGP BFD also doesn't seem to work when update source is a loopback interface. Thus there doesn't seem to be BFD support for this setup.

[Andrea Florio]

BFD is not supported on unnumbered interfaces on NX-OS 7

There is no reference of it in NX-OS 9.2 or 9.3, furthermore, all previous versions worked flawlessly.

this doesn't only effect IS-IS but also OSPF when running unnumbered, to be honest i'm expecting the vast majority of  deployments to be running with IS-IS or OSPF unnumbered in the underlay.

furthermore, in the official configuration guides you can see unnumbered with BFD

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/93x/vxlan/configuration/guide/b-cisco-nexus-9000-series-nx-os-vxlan-configuration-guide-93x/b-cisco-nexus-9000-series-nx-os-vxlan-configuration-guide-93x_appendix_010101.html

this is definitely not a sev 6 bug, but a much higher sev, i'd even call it a sev 2 because multiple of our datacenters are not protect agaist fast failure detection

[JasperHorng9198]

Also interesting is bfd on unnumbered interfaces is supported on Nexus 7000 series switches. I am making an assumption, but couldn't that implementation be ported over to Nexus 9000 easily?

[Andrea Florio]

we cannot know if we don't know the code or hardware architecture properly but i'm with you.

The only chance we have is to reach to our cisco contacts and push for this feature request.

i'll definitely do that

[Cameron Buie]

Hey Andrea,

It looks we'll be bringing the functionality in release 10.1(1). Which should release early 2021.

Hope that's useful information for you.

- Cameron