Got a chance to test this. The RR will reflect the best path based on it's own local view of the world. Thus, if everything is equal for a collection of advertisements to X, the RR will compute it's IGP cost to each next-hop, and select the next-hop that it is closest to. This path is then reflected to all clients.
While I didn't confirm this with two RRs, it seems that it might make sense for the RRs to be at different parts of the network so that each might generate different best paths which are then reflected to the clients. Clients then can select between those two paths as to which is closest. bergenpeak wrote: > > Question about route reflector operation. > > It appears that a RR, when provided with multiple routes to the > same destination, will pick the best path and then reflect this > best path to the appropriate set of clients and non-clients. > > I had expected that the RR would simply just reflect routes and > not perform route selection on behalf of clients. While this does > have benefits to lower-end RR clients, I'm curious as to how step > 8 of the BGP decision process is made. Step 8 is where an iBGP > router, for a set of equal routes, will compute the IGP cost to > the route's next-hop, and select the path whose next-hop is IGP > closest. > > How is this step performed by the RR? Does the RR compute the > IGP cost from itself to the next-hop, or does it attempt to > compute the IGP cost from each client to the next-hop? I get > the impression that it is the former (RR to nexthop). If this > is correct, then might one expect sub-optimal BGP routes selection > at times as the cost is from the RR to the next-hop and not the > real cost from an iBGP client to the next-hop? > > Much like aggregation, some sub-optimalities might be the price > paid to scale. Just trying to verify how path selection is > handled when RR's are present. > > Thanks Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=62312&t=61900 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
