[c-nsp] OSPF on Ring Networks

[Christian Meutes]

On Sat, 14 May 2011 17:50:39 +0100, Nick Hilliard <nick at foobar.org> wrote:

> yes if the next-hop changes, but network topology change events will
often 
> not cause a next-hop change, just a SFP recalculation - which means that
> if 
> your SFP domain is smaller, it will converge faster.  I.e. the router's
> FIB 
> may be updated, but ibgp will not be aware of the topology change.
> 
> The things that cause next-hop changes are customer edge flaps.

Not only customer-link flaps, but also every downtime of any of your
routers which terminates BGP routes, eg. all edge-routers.

> As regards carrying non-infrastructure prefixes in OSPF, it really
depends 
> on how big your network is.  For small networks it doesn't matter very 
> much.  For large networks, there is no choice other than ibgp because 
> having a functional prefix management system is more important than
> shaving 
> a couple of seconds off a customer edge link-up event.  For networks in
> the 
> middle, they usually start out by putting non-infrastructural prefixes
> into 
> the IGP but change later on because it doesn't scale well and having a 
> flexible interior routing policy becomes more important than fast
> convergence.

Yes, but we are talking about network of 11 routers. :-)