Technical data

BMD00136, November 2009 131
CHAPTER 10
Border Gateway Protocol
Border Gateway Protocol (BGP) is an Internet protocol that enables routers on a network to share
and advertise routing information with each other about the segments of the IP address space they
can access within their network and with routers on external networks. BGP allows you to decide
what is the “best” route for a packet to take from your network to a destination on another network
rather than simply setting a default route from your border router(s) to your upstream provider(s).
BGP is defined in RFC 1771.
RackSwitch G8000s can advertise their IP interfaces and IP addresses using BGP and take BGP
feeds from as many as 16 BGP router peers. This allows more resilience and flexibility in balancing
traffic from the Internet.
The following topics are discussed in this section:
 “Internal Routing Versus External Routing” on page 131
 “Forming BGP Peer Routers” on page 133
 “What is a Route Map?” on page 133
 “Aggregating Routes” on page 137
 “Redistributing Routes” on page 137
 “BGP Attributes” on page 138
 “Selecting Route Paths in BGP” on page 139
 “BGP Failover Configuration” on page 140
 “Default Redistribution and Route Aggregation Example” on page 142
Internal Routing Versus External Routing
To ensure effective processing of network traffic, every router on your network needs to know how
to send a packet (directly or indirectly) to any other location/destination in your network. This is
referred to as internal routing and can be done with static routes or using active, internal dynamic
routing protocols, such as RIP, RIPv2, and OSPF.