BGP RR Cluster-ID's Benefits & Cons?

Imagine you had a topology of this:


Client 1 and 2 are part of RR1

Client 3 and 4 are part of RR2

Very Simple


The question now is whether to configure the same cluster-id or not. So I want to evaluate the pro's and cons of configuring the same cluster-id, but I can only see cons at the moment. This is why:


If we use the same cluster-id on both RR's then any routes reflected from RR1 towards RR2 (and visa versa) would be dropped because of cluster-id being the same. This means that there would be a latency and CPU performance overhead of RR1 for sending the prefixes over to RR2, and then a CPU performance overhead of RR2 dropping the routes.However if different cluster-id's were used it means that either RR could actually install these prefixes which would only add a bit more memory requirements to install the routes. That is it! So why would you want to use the same cluster-id?


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