Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Route reflectors

Route reflectors (RRs) reorganize the IBGP core into a hierarchy and allow route advertisement rules. Route reflection divides IBGP peers into two groups — client peers and nonclient peers.

• If a route is received from a nonclient peer, it reflects the route to all client peers
• If a route is received from a client peer, it reflects the route to all nonclient and client peers

An RR and its client peers form a route reflection cluster. BGP speakers announce only the best route for a given prefix. RR rules apply after the router makes its best path decision.

Routers B, C, D, E, and G are members of the same AS—AS100. These routers are also in the same route reflection cluster, where Router D is the route reflector. Routers E and G are client peers of Router D, and Routers B and C and nonclient peers of Router D.

1. Router B receives an advertisement from Router A through EBGP. Because the route is learned through EBGP, Router B advertises it to all its IBGP peers — Routers C and D.
2. Router C receives the advertisement but does not advertise it to any peer because its only other peer is Router D (an IBGP peer) and Router D has already learned it through IBGP from Router B.
3. Router D does not advertise the route to Router C because Router C is a nonclient peer. The route advertisement came from Router B which is also a nonclient peer.
4. Router D does reflect the advertisement to Routers E and G because they are client peers of Router D.
5. Routers E and G advertise this IBGP learned route to their EBGP peers — Routers F and H.