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Specifying the AS Path

By default, no AS path information is associated with generated routes. To associate AS path information with the routes, include the as-path statement:




as-path <as-path> <origin (egp | igp | incomplete)> <atomic-aggregate> <aggregator as-number in-address>;

For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.

as-path is the AS path to include with the route. It can include a combination of individual AS path numbers and AS sets. Enclose sets in brackets ( [ ] ). The first AS number in the path represents the AS immediately adjacent to the local AS. Each subsequent number represents an AS that is progressively farther from the local AS, heading toward the origin of the path.

Note: Beginning with JUNOS Release 9.1, the numeric AS range has been extended to provide BGP support for 4-byte AS numbers, as defined in RFC 4983, BGP Support for Four-octet AS Number Space. For the AS number, you can now configure a number from 1 through 4,294,967,295.

You also can specify the AS path using the BGP origin attribute, which indicates the origin of the AS path information:

egp—Path information originated in another AS.
igp—Path information originated within the local AS.
incomplete—Path information was learned by some other means.

To attach the BGP ATOMIC_AGGREGATE path attribute to the generated route, specify the atomic-aggregate option. This path attribute indicates that the local system selected a less specific route rather than a more specific route.

To attach the BGP AGGREGATOR path attribute to the generated route, specify the aggregator option. When using this option, you must specify the last AS number that formed the generated route (encoded as two octets), followed by the IP address of the BGP system that formed the generated route.

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