Concept Guide

To illustrate how these rules aect 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 Reection Cluster, where Router D is the Route Reector. Router E and
H are client peers of Router D; Routers B and C and nonclient peers of Router D.
Figure 24. 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 reect 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.
Conguring BGP Route Reectors
BGP route reectors are intended for ASs with a large mesh; they reduce the amount of BGP control trac.
NOTE
: Dell EMC Networking recommends not using multipath and add path simultaneously in a route reector.
With route reection congured properly, IBGP routers are not fully meshed within a cluster but all receive routing information.
Congure clusters of routers where one router is a concentration router and the others are clients who receive their updates from the
concentration router.
To congure a route reector, use the following commands.
• Assign a cluster ID or an IP address to a router reector cluster.
CONFIG-ROUTER-BGP mode
bgp cluster-id ip-address | number
– ip-address: IP address as the route reector cluster ID.
– number: A route reector 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 reector, the cluster ID is the route reector’s
router ID. For redundancy, a BGP cluster may contain two or more route reectors. Without a cluster ID, the route reector cannot
recognize route updates from the other routes reector within the cluster.
• Congure the local router as a route reector and the specied 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 rst time, the router congures as a route reector and the specied BGP neighbors congure as
clients in the route reector cluster. When you remove all clients of a route reector using the no neighbor route-reflector-
client command, the router no longer functions as a route reector. When you enable a route reector, Dell EMC Networking OS
Border Gateway Protocol (BGP)
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