8.7.3 AS_PATH Attribute Aggregation

When a summarized route includes a BGP4 route among its source routes, the summarized route is tagged with the path attribute of the BGP4 route. If the source routes include more than one BGP4 route, the path attributes are summarized among those routes. The AS_PATH and COMMUNITIES attributes of summarized routes are edited as follows:

<Structure of this section>

(1) AS_PATH attribute

The initial AS path segment within the AS_SEQUENCE type of the AS_PATH attribute which is common to the summarization source routes is assigned as the AS_SEQUENCE type of the AS_PATH attribute of the summarized route. All other AS paths in the AS_SEQUENCE type and those outside the AS_SEQUENCE type appear in the AS_SET type of the AS_PATH attribute of the summarized route only if you execute the ip summary-address configuration command with the as_set parameter specified.

(2) COMMUNITIES Properties

Every community in the summarization source BGP4 routes is set to the COMMUNITIES attribute of the summarized route.