Bgp Routing Domain Confederation; Configure Routing Domain Confederation For Bgp - Cisco NCS 5500 Series Configuration Manual

BGP Routing Domain Confederation

Step 4
commit
BGP Routing Domain Confederation
One way to reduce the iBGP mesh is to divide an autonomous system into multiple sub-autonomous systems
and group them into a single confederation. To the outside world, the confederation looks like a single
autonomous system. Each autonomous system is fully meshed within itself and has a few connections to other
autonomous systems in the same confederation. Although the peers in different autonomous systems have
eBGP sessions, they exchange routing information as if they were iBGP peers. Specifically, the next hop,
MED, and local preference information is preserved. This feature allows you to retain a single IGP for all of
the autonomous systems.

Configure Routing Domain Confederation for BGP

Perform this task to configure the routing domain confederation for BGP. This includes specifying a
confederation identifier and autonomous systems that belong to the confederation.
Configuring a routing domain confederation reduces the internal BGP (iBGP) mesh by dividing an autonomous
system into multiple autonomous systems and grouping them into a single confederation. Each autonomous
system is fully meshed within itself and has a few connections to another autonomous system in the same
confederation. The confederation maintains the next hop and local preference information, and that allows
you to retain a single Interior Gateway Protocol (IGP) for all autonomous systems. To the outside world, the
confederation looks like a single autonomous system.
SUMMARY STEPS
1. configure
2. router bgp as-number
3. bgp confederation identifier as-number
4. bgp confederation peers as-number
5. commit
DETAILED STEPS
Step 1 configure
Step 2 router bgp as-number
Example:
RP/0/RP0/CPU0:router# router bgp 120
Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP
routing process.
Step 3 bgp confederation identifier as-number
BGP Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
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Implementing BGP