Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual page 183

From router Mason's perspective, router Boston is simply a member of AS 29:
bgp confederation identifier
bgp confederation peers
ip bgp-confed-as-set new-format
host3(config-router)#neighbor 10.2.25.6 remote-as 29
host4(config)#router bgp 413
host4(config-router)#neighbor 10.3.3.2 remote-as 29
Use to establish a router as a member of the specified BGP confederation.
To routers outside the confederation, the confederation appears as an autonomous
system with an AS number the same as the confederation identifier.
The new confederation identifier is used in open messages and in the AS path
in update messages that are sent after you issue the command.
To force sessions that are already up to use the new confederation identifier,
you must use the clear ip bgp command to perform a hard clear.
Use the no version to remove the sub-AS from the confederation.
See bgp confederation identifier.
Use to enable EBGP sessions with routers in the peer sub-ASs; the EBGP sessions
preserve local-pref, MED, and next-hop attributes.
You can specify one or more individual sub-AS numbers, or you can issue the
filter-list keyword and an AS-path access list (which is based on regular
expressions) to specify a list of sub-AS numbers.
If the remote AS of a peer appears in the specified list of sub-ASs or is identified
by the filter list, then the peer is treated as being in the same confederation.
This command takes effect immediately and bounces only those sessions whose
peer type changed as a result of issuing the command.
Use the no version to remove individually specified sub-ASs, all sub-ASs specified
by the filter list, or all sub-ASs from the confederation.
See bgp confederation peers.
Use to specify that AS-confed-sets are displayed enclosed within square brackets
rather than parentheses, and that the AS paths in the set are delimited by commas
rather than spaces.
Example
host1(config)#ip bgp-confed-as-set new-format
Use the no version to restore the default display within parentheses and with
space-delimited ASs.
See ip bgp-confed-as-set new-format.
Chapter 1: Configuring BGP Routing
Managing a Large-Scale AS
147