1. Scaling Service Provider Networks
Configuring and Monitoring Confederations

2. Outline Overview BGP Confederation Design Rules
Planning BGP Confederations
Configuring BGP Confederations
Monitoring BGP Confederations
Summary

3. BGP Confederation Design Rules
IBGP full mesh within each member-AS is required.
Route reflectors might be used within each AS to relax the IBGP full-mesh requirements.
There is no topology limitation on EBGP sessions between autonomous systems within a confederation.
The intra-confederation EBGP sessions will follow the physical topology of the network.

4. Planning BGP Confederations
Divide the transit AS into smaller areas.
Follow the physical topology of the network.
Define the AS number for each area.
Use AS numbers reserved for private use (64512 – 65535).
Verify the Cisco IOS release level.
All routers have to support BGP confederations.
Convert each area into an AS.
A total rewrite of the BGP configuration is required.

5. Configuring BGP Confederations
Start the BGP process with the member-AS number.
Specify an external AS number.
Must be defined in all routers within confederation
List all member-AS numbers in the confederation.
Must be defined in all routers with an EBGP session

6. Configuring BGP Confederations (Cont.)
router(config)#
no router bgp as-number
router bgp member-as-number
Removes old BGP process and configures BGP process with member-AS number
router(config-router)#
bgp confederation identifier external-as-number
Configures external confederation-wide AS number
router(config-router)#
bgp confederation peers list-of-intra-confederation-as
Defines all the other autonomous systems in the confederation

7. Configuring BGP Confederations—Sample Configuration

8. Monitoring BGP Confederations
router>
show ip bgp neighbors
Displays whether a neighbor is within the confederation
router>
show ip bgp prefix [mask]
Displays internal and external segments of the AS-path attribute
Displays whether the path is external, internal, or intra-confederation external

9. Monitoring Intra-Confederation EBGP Neighbors

10. Monitoring Confederation Routes

11. Summary
BGP confederations do not modify IBGP behavior; thus, the classic IBGP split-horizon rules still apply, and a full mesh of IBGP sessions between all routers in the member AS is still required.
A proper migration plan is important because the change to BGP confederation involves a major reconfiguration of BGP routing.
BGP confederations are configured by specifying the confederation identifier and other member-AS peers.
The show ip bgp neighbors command has been modified to display whether a BGP neighbor is part of a BGP confederation.