BGP multi-layer route-reflecrtor topology

[Konstantin Dunaev]

Hello,

I'm trying to figure out if the multi-layer Route-Reflector topology would work for me. Let say we have 2 Route-reflectors RC-RR1 and RC-R2 and all other router are their reflect-clients. Now I'm getting a new router RC-.E001 and would like to set new level of Route-reflectors. I'd like that now the router  RC-E001 is a route-reflector client of RC-E002 (new level of RR) and RC-RR1, e.g. it will be a client of route-reflectors from different levels.

Is it possible? Which problems can arised?

[lgijssel]

Interesting question, although it will be much work to provide a truly detailed answer.

After looking at it briefly, my conclusion is this:

The resulting config will be invalid because any new router which is added to the AS must have a full mesh with all routers which are not route reflector clients. So RC-E002 will need bgp neighbor statements for both RC-RR1 and RC-RR2.

If this condition is not satisfied, inpredictable behavior will result (sub-optimal routing and non-functional redundancy).

The theory behind route reflectors is described in quite some detail in:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml#routereflectors

If you really want to go into the details, best is to build the setup in a lab (GNS3).

regards,

Leo

[Konstantin Dunaev]

Thank you for the link, I've read it already

this link is interesting as well

http://blog.sazza.de/?cat=22

you wrote: "RC-E002 will need bgp neighbor statements for both RC-RR1 and RC-RR2. "

of course BGP session stays between them, only change which I'd like to do is to add a new RC-E001 router as route-reflector client.

RC-E001 should be route-reflector client for RC-E002 and RC-RR1. It's not a problem to make it as route-reflector client for one of them, but for both in the same time - I'm not sure if it is allowed, because RC-E002 itself is a route-reflector client for RC-RR1

[lgijssel]

Konstantin Dunaev wrote:
RC-E001 should be route-reflector client for RC-E002 and RC-RR1. It's not a problem to make it as route-reflector client for one of them, but for both in the same time - I'm not sure if it is allowed, because RC-E002 itself is a route-reflector client for RC-RR1

Which is why it has no purpose to do this. The main objective for using RR is to reduce the number of BGP peers.

Leo