White Papers

● 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.
Enabling Route Flap Dampening
When EBGP routes become unavailable, they “flap” and the router issues both WITHDRAWN and UPDATE notices.
A flap 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● is withdrawn
● is readvertised after being withdrawn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The constant router reaction to the WITHDRAWN and UPDATE notices causes instability in the BGP process.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 configure penalties (a numeric value) for routes that flap. When that penalty value reaches a configured
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 flap, the penalty value decrements or is decayed. However, if the route flaps again, it is assigned another
penalty.
The penalty value is cumulative and penalty is added under following cases:
● Withdraw
● Readvertise
● Attribute change
When dampening is applied to a route, its path is described by one of the following terms:
● history entry — an entry that stores information on a downed route
● dampened path — a path that is no longer advertised
● penalized path — a path that is assigned a penalty
To configure route flap dampening parameters, set dampening parameters using a route map, clear information on route
dampening and return suppressed routes to active state, view statistics on route flapping, or change the path selection from the
default mode (deterministic) to non-deterministic, use the following commands.
● Enable route dampening.
CONFIG-ROUTER-BGP mode
bgp dampening [half-life | reuse | suppress max-suppress-time] [route-map map-name]
Enter the following optional parameters to configure route dampening parameters:
○ half-life: the range is from 1 to 45. Number of minutes after which the Penalty is decreased. After the router assigns
a Penalty of 1024 to a route, the Penalty is decreased by half after the half-life period expires. The default is 15 minutes.
○ reuse: the range is from 1 to 20000. This number is compared to the flapping route’s Penalty value. If the Penalty value
is less than the reuse value, the flapping route is once again advertised (or no longer suppressed). Withdrawn routes are
removed from history state. The default is 750.
202
Border Gateway Protocol (BGP)