BGP Features
ExtremeWare XOS 11.3 Concepts Guide
571
configure vlan to_rr add port 1:1
configure vlan to_rr ipaddress 30.0.0.1/24
enable ipforwarding vlan to_rr
configure bgp router 4.4.4.4
configure bgp as-number 100
create bgp neighbor 30.0.0.2 remote-as 100
enable bgp neighbor all
enable bgp
Route Confederations
BGP requires networks to use a fully meshed router configuration. This requirement does not scale well,
especially when BGP is used as an IGP. One way to reduce the size of a fully meshed AS is to divide the
AS into multiple sub-ASs and to group these sub-ASs into a routing confederation. Within the
confederation, each sub-AS must be fully meshed. The confederation is advertised to other networks as
a single AS.
Route Confederation Example
Figure 77 shows an example of a confederation.
Figure 77: Routing confederation
In this example, AS 200 has five BGP speakers. Without a confederation, BGP would require that the
routes in AS 200 be fully meshed. Using the confederation, AS 200 is split into two sub-ASs: AS65001
and AS65002. Each sub-AS is fully meshed, and IBGP is running among its members. EBGP is used
between sub-AS 65001 and sub-AS 65002. Router B and router D are EBGP peers. EBGP is also used
between the confederation and outside ASs.
EX_043
EBGP
SubAS 65001
SubAS 65002
EBGP
AS 200
IBGP
IBGP
AB
C
192.1.1.6/30 192.1.1.5/30 192.1.1.9/30
192.1.1.17/30
192.1.1.18/30
192.1.1.21/30
192.1.1.22/30
DE
192.1.1.13/30
192.1.1.10/30
192.1.1.14/30
EBGP
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