Is there any/sufficient benefit in adding BFD onto BGP sessions between
directly-connected routers? If we have intermediate L2 devices such that we can't reliably detect link failures BFD can help us quickly detect peers going away even when link remains up, but what about sessions with:
- eBGP with peering to interface addresses (not loopback)
- no multi-hop
- direct back-to-back connections (no intermediate devices except patch panels)
Possible failure scenarios where I could see this helping would be fat fingering (filters implemented on one or the other side drops traffic from the peer) or e.g. something catastrophic that causes the control plane to go away without any last gasp to the peer.
Or is adding BFD into the mix in this type of setup getting into increasing effort/complexity (an additional protocol) for dimishing returns?
I've used this configuration in a past line when I may of had multiple L2
steps between L3 devices. The only concern we had was around load BFD put
on _some_ endpoint routers, if was handles on the RouteProcessor vs on line
cards.
Hugo, I think those are all valid potential reasons to use BFD. I use it
for some of the same reasons even on direct connect peers.
Only time I ever recall actively avoiding it if I had the capability was if
I had NSF/SSO, since they didn't used to (still don't?) play very well
together.
- eBGP with peering to interface addresses (not loopback)
- no multi-hop
- direct back-to-back connections (no intermediate devices except patch
panels)
Possible failure scenarios where I could see this helping would be fat
fingering (filters implemented on one or the other side drops traffic from
the peer) or e.g. something catastrophic that causes the control plane to go
away without any last gasp to the peer.
Or is adding BFD into the mix in this type of setup getting into increasing
effort/complexity (an additional protocol) for dimishing returns?
If you have HW liveliness detection and fast-failover, I think BFD
probably will just reduce availability due its failures being more
probable than the edge cases in your setup.
I personally would not run BFD here.