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To illustrate how these rules affect routing, refer to the following illustration and the following steps. 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. Router E and H are client peers of Router D; Routers B and C and nonclient peers of Router D.
Figure 25. BGP Router Rules
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 and the route advertisement came
from Router B who 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 then advertise this iBGP learned route to their eBGP peers Routers F and H.
Configuring BGP Route Reflectors
BGP route reflectors are intended for ASs with a large mesh; they reduce the amount of BGP control traffic.
NOTE: Dell EMC Networking recommends not using multipath and add path simultaneously in a route reflector.
With route reflection configured properly, IBGP routers are not fully meshed within a cluster but all receive routing information.
Configure clusters of routers where one router is a concentration router and the others are clients who receive their updates
from the concentration router.
To configure a route reflector, use the following commands.
● Assign a cluster ID or an IP address to a router reflector cluster.
CONFIG-ROUTER-BGP mode
bgp cluster-id ip-address | number
○ ip-address: IP address as the route reflector cluster ID.
○ number: A route reflector cluster ID as a number from 1 to 4294967295.
You can have multiple clusters in an AS. When a BGP cluster contains only one route reflector, the cluster ID is the route
reflector’s router ID. For redundancy, a BGP cluster may contain two or more route reflectors. Without a cluster ID, the
route reflector cannot recognize route updates from the other routes reflector within the cluster.
● Configure the local router as a route reflector and the specified neighbors or peer group as members of the cluster.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} route-reflector-client
When you enter this command for the first time, the router configures as a route reflector and the specified BGP neighbors
configure as clients in the route reflector cluster. When you remove all clients of a route reflector using the no neighbor
route-reflector-client command, the router no longer functions as a route reflector. When you enable a route reflector,
Dell EMC Networking OS automatically enables route reflection to all clients. To disable route reflection between all clients in
this reflector, use the no bgp client-to-client reflection command in CONFIGURATION ROUTER BGP mode. All
clients must be fully meshed before you disable route reflection.
To view a route reflector configuration, use the show config command in CONFIGURATION ROUTER BGP mode or the
show running-config bgp in EXEC Privilege mode.
Border Gateway Protocol (BGP)
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