[c-nsp] Faster iBGP convergance: Tune the timers or use Fast Peering Session Deactivation?

[Richard A Steenbergen]

On Tue, Jun 08, 2010 at 05:14:58PM +0100, Sam Stickland wrote:
> All,
> 
> I'd appreciate any feedback people have on tuning iBGP for faster
> convergence, particularly dead peer detection for indirect Loopback to
> Loopback peerings.
...
> I heard via some other colleges that Cisco do not recommend FPD due to IGP
> instability promoting BGP instability and if we do run into issues with
> FPD in production, Cisco will recommend we remove it opposed to a productive
> TAC case being endeavoured.

Ideally you wouldn't actually want IBGP to fail, you'd want the next-hop
the IBGP session points to to fail, thus invaliding the paths to the
prefixes (especially if you're running code with next-hop indirection
support). Tearing down the IBGP session accomplishes nothing but burning
a lot of time and cpu resources bringing it back up later on. If your
next-hop goes away in IGP you can pull the prefixes from use without
having to actually kill IBGP quickly, and if you have next-hop
indirection you can pull the prefixes in a single operation, which 
should vastly improve convergence times.

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)