Configuring a confederation

Reducing a complicated IBGP mesh can be accomplished by dividing a large autonomous system into smaller autonomous systems. The smaller ASs can be grouped into a confederation. A confederation looks like a single AS to routers outside the confederation. Each confederation is identified by its own (confederation) AS number.

To configure a BGP confederation, you must specify a confederation identifier, an AS number expressed as a decimal integer. The collection of autonomous systems appears as a single autonomous system with the confederation number acting as the ‟all-inclusive” autonomous system number. Up to 15 members (ASs) can be added to a confederation.

The confederation command is configured in the config>router context.

Use the following CLI syntax to configure a confederation.

CLI syntax

config>router# confederation confed-as-num members 
       member-as-num

When 4-byte AS number support is not disabled on router, the confederation and any of its members can be assigned an AS number in the range from 1 to 4294967295. The following example displays a confederation configuration command usage.

Example

config>router># confederation 1000 members 100 200 300

The following example displays the confederation configuration:

ALA-B>config>router# info
#------------------------------------------
# IP Configuration
#------------------------------------------
        interface "system"
            address 10.10.10.103/32
        exit
        interface "to-104"
            shutdown
            address 10.0.0.103/24
            port 1/1/1
        exit
        autonomous-system 100
        confederation 1000 members 100 200 300
        router-id 10.10.10.103
#------------------------------------------
ALA-B>config>router#