ECS4660-28F_Management Guide-R03

C HAPTER 51 | IP Routing Commands
Border Gateway Protocol (BGPv4)
– 1842 –
COMMAND USAGE
◆ A cluster of clients will usually have a single route reflector (RR). In
that case, the cluster can be identified by the BGP Identifier of the RR.
However, this represents a single point of failure. This command is used
to designate multiple route reflectors used within the same cluster so
that they can recognize updates from other peer route reflectors and
discard them to prevent loopbacks.
◆ All the route reflectors in the same cluster should be fully meshed and
all of them configured with identical sets of client and non-client peers.
◆ A route reflector uses the non-transitive cluster-list attribute to avoid
routing loops. A cluster-list is a sequence of cluster IDs the route has
passed through. When a RR reflects a route from its clients to non-
client peers, and vice versa, it appends this ID to the cluster list. Using
this attribute, an RR can determine if routing information has looped
back to the same cluster due to mis-configuration. If the local cluster
ID is found in the cluster list, the advertisement is ignored.
EXAMPLE
Console(config-router)#bgp cluster-id 192.168.0.0
Console(config-router)#
RELATED COMMANDS
bgp client-to-client reflection (1840)
bgp confederation
identifier
This command configures the identifier for a confederation containing
smaller multiple internal autonomous systems, and declares this router as
a member of the confederation. Use the no form to remove the
confederation identifier.
SYNTAX
bgp confederation identifier as-number
no bgp confederation identifier
as-number – Autonomous system number which identifies this
router as a member of the specified domain, and tags routing
messages passed to other BGP routers with this number.
(Range: 1-4294967295)
COMMAND MODE
Router Configuration
DEFAULT SETTING
No confederation identifier is configured.
COMMAND USAGE
◆ BGP confederations are used to reduce the requirement for fully
meshed connections between iBGP peers in the same AS. It works by