Specifications

BGP Features
ExtremeWare XOS 11.0 Concepts Guide 293
BGP Features
This section describes the following BGP features supported by ExtremeWare XOS:
• Route Reflectors on page 293
• Route Confederations on page 295
• Route Aggregation on page 298
• Using the Loopback Interface on page 298
• BGP Peer Groups on page 298
• BGP Route Flap Dampening on page 299
• BGP Route Selection on page 301
• Route Redistribution on page 301
• BGP Static Network on page 302
Route Reflectors
Another way to overcome the difficulties of creating a fully meshed AS is to use route reflectors. Route
reflectors allow a single router to serve as a central routing point for the AS.
A cluster is formed by the route reflector and its client routers. Peer routers that are not part of the
cluster must be fully meshed according to the rules of BGP.
A BGP cluster, including the route reflector and its clients, is shown in Figure 53.
Figure 53: Route reflectors
The topology shown in Figure 53 minimizes the number of BGP peering sessions required in an AS by
using route reflectors.
In this example, although the BGP speakers 3.3.3.3 and 4.4.4.4 do not have a direct BGP peering session
between them, these speakers still receive routes from each other indirectly through 2.2.2.2. The router
2.2.2.2 is called a route reflector and is responsible for reflecting routes between its clients. Routes
EX_042
Client
Client
Route Reflector
Non-client
10.0.0.1
10.0.0.2
30.0.0.1
30.0.0.2
20.0.0.2
20.0.0.1
1.1.1.1
2.2.2.2
4.4.4.4
3.3.3.3
Cluster
AS 100