Administrator's Guide v4.1.1 Manual

FIGURE 74 BGP with multiple VCS clusters and autonomous systems
The figure below illustrates a BGP topology that incorporates a route-reflector server and route-
reflector clients.
FIGURE 75 BGP route-reflector server and clients
BGP peering
Unlike OSPF or other IGP protocols, BGP does not have neighbor detection capability. BGP neighbors
(or peers) must be configured manually. A router configured to run BGP is called a BGP "speaker." A
BGP speaker connects to another speaker (either in the same or a different AS) by using a TCP
connection to port 179 (the well-known BGP port), to exchange the routing information. The TCP
connection is maintained throughout the peering session. While the connection between BGP peers is
alive, two peers communicate by means of the following types of messages:
• OPEN
• UPDATE
BGP peering
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