Bgp route reflector12/2/2023 That significantly ease the scalability of the BGP infrastructure. Any new router in the network topology needs only to create a session with route reflector and it will get all routes from there. It has the capability of advertising routes between internal BGP peers. Route reflector explained iBGP full mesh topology iBGP topology with route reflectorĪ Route reflector is a router that acts as a routing information exchange server for all other iBGP routers. This is the formula for calculating the number of sessions needed for a full mesh: Simply said, all iBGP peers need to form neighborship with all other iBGP routers. None of the routes received from one iBGP peer can be advertised or forwarded to another iBGP peer. The AS number for iBGP peers is the same so the BGP protocol needed to adopt a special rule. This loop prevention mechanism is perfectly logical for Internet routes (eBGP), however it limits the scalability with internal BGP peerings (iBGP). When a router sees the same AS number as its own in the route, it knows that it’s coming from its own autonomous system and doesn’t use it because it would generate a loop. With external BGP (connection between different autonomous systems) there’s a simple solution to avoid routing loops, which is the autonomous system number that is added to each route and describes its origin. Why is route reflecting so helpful when it comes to scalability? First, we need to look at how routes are exchanging information via the BGP protocol. It’s very important to be familiar with BGP protocol prior getting involved with route reflectors. The complete route reflector concept can be found in RFC4456, which dates back to 2006. It would be hard to imagine multiple routers running BGP in full mesh topology these days when scalability is the key. Route reflectors became an essential part of any larger internet service provider’s environment.
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