3Com 7700 Configuration Manual page 137

Two Kinds of Measures to Avoid Looping Inside AS As route reflector is
imported, it is possible that path looping will be generated in AS. Path update
packets already left the cluster may attempt to return to the cluster. The
conventional AS path method can't detect the internal AS looping, because the
path update packet hasn't left AS.
Upon configuring route reflector, BGP provides the following measures to avoid
internal AS looping:
Configure the Originator_ID of the route reflector
■
Configure the Cluster_ID of the route reflector
■
The Originator_ID is established by route reflector. The originator will drop the
update packet returning to the originator should it be improper configuration.
The parameter is not necessarily configured, and it will automatically function
upon enabling BGP.
Configuring BGP AS Confederation Attributes
Confederation provides the method to handle the booming IBGP network
connections inside AS. It divides the AS into multiple sub-AS, in each of which all
IBGP peers are fully connected, and are connected with other sub-AS of the
confederation.
Note that the route must be re-configured upon switching from
non-confederation to confederation solution, and that the logic topology be
basically changed. Furthermore, the path selected by confederation may not be
the best path if there is no manually-set BGP policy.
Configuring confederation_ID In the eye of the BGP speakers that are not
included in the confederation, multiple sub-ASs that belong to the same
confederation are a whole. The external network does not need to know the
status of internal sub-ASs, and the confederation ID is the AS number identifying
the confederation as a whole.
Perform the following configurations in BGP view.
Table 111 Configuring confederation_ID
Operation
Configure confederation_ID
Canceling confederation_ID
By default, the confederation_ID is not configured.
Configuring the Sub-AS of the Confederation Configure confederation_ID
first, and then configure the sub-AS belonging to the confederation. One
confederation includes up to 32 sub-ASs. The as-number used upon configuring
sub-AS belonging to the confederation is valid within the confederation.
Command
confederation id as-number
undo confederation id
BGP 129