IBGP Question --- Router Reflector or iBGP Mesh

Iljitsch van Beijnum iljitsch at muada.com
Tue Jan 11 13:10:04 UTC 2005

On 11-jan-05, at 12:51, Philip Smith wrote:

> Well, my preference is to start with route reflectors pretty much from 
> day one. Let's face it, one day you will have to migrate that full 
> mesh iBGP to route reflector. Why do the work of migration when you 
> can start off at the beginning using route reflectors. One less job to 
> do, one less potential network disruption, happy customers,...

You're assuming it's disruptive to add route reflection...

The trouble with doing this very early is that the reflectors may end 
up in inconvenient places. And since you need at least two for 
redundancy, you don't save much in a three or four router setup.

> As for guidelines for transition, check out the BGP tutorials which 
> have been given at the recent NANOGs. It's really very simple to do, 
> and you are lucky as you have relatively few routers to migrate.

Yup, very simple: just create two peergroups on the reflectors: one for 
reflectors and permanently non-client peers and another one for 
clients. Then assign iBGP peers to the peergroups and you're done. 
You'll still have some now unnecessary iBGP links between clients but 
that's ok: no need to remove them.

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