Concept Guide

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
automatically enables route reection to all clients. To disable route reection between all clients in this reector, use the no bgp
client-to-client reflection
command in CONFIGURATION ROUTER BGP mode. All clients must be fully meshed before you
disable route reection.
To view a route reector conguration, use the show config command in CONFIGURATION ROUTER BGP mode or the show
running-config bgp
in EXEC Privilege mode.
Enabling Route Flap Dampening
When EBGP routes become unavailable, they “ap” and the router issues both WITHDRAWN and UPDATE notices.
A ap is when a route:
• is withdrawn
• is readvertised after being withdrawn
• has an attribute change
The constant router reaction to the WITHDRAWN and UPDATE notices causes instability in the BGP process. To minimize this instability,
you may congure penalties (a numeric value) for routes that ap. When that penalty value reaches a congured limit, the route is not
advertised, even if the route is up. In Dell EMC Networking OS, that penalty value is 1024. As time passes and the route does not ap, the
penalty value decrements or is decayed. However, if the route aps again, it is assigned another penalty.
The penalty value is cumulative and penalty is added under following cases:
240
Border Gateway Protocol (BGP)