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as-path (Routing Options)



Hierarchy Level

Release Information

Statement introduced before Junos OS Release 7.4.


Associate BGP autonomous system (AS) path information with a static, aggregate, or generated route.

In Junos OS Release 9.1 and later, the numeric range for the AS number is extended to provide BGP support for 4-byte AS numbers as defined in RFC 4893, BGP Support for Four-octet AS Number Space. RFC 4893 introduces two new optional transitive BGP attributes, AS4_PATH and AS4_AGGREGATOR. These new attributes are used to propagate 4-byte AS path information across BGP speakers that do not support 4-byte AS numbers. RFC 4893 also introduces a reserved, well-known, 2-byte AS number, AS 23456. This reserved AS number is called AS_TRANS in RFC 4893. All releases of Junos OS support 2-byte AS numbers.

In Junos OS Release 9.2 and later, you can also configure a 4-byte AS number using the AS-dot notation format of two integer values joined by a period: <16-bit high-order value in decimal>.<16-bit low-order value in decimal>. For example, the 4-byte AS number of 65,546 in plain-number format is represented as 1.10 in the AS-dot notation format. You can specify a value in the range from 0.0 through 65535.65535 in AS-dot notation format.


No AS path information is associated with static routes.


aggregator—(Optional) Attach the BGP aggregator path attribute to the aggregate route. You must specify the last AS number that formed the aggregate route (encoded as two octets) for as-number, followed by the IP address of the BGP system that formed the aggregate route for ip-address.

as-path—(Optional) 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. You cannot specify a regular expression for as-path. You must use a complete, valid AS path.

atomic-aggregate—(Optional) Attach the BGP atomic-aggregate path attribute to the aggregate route. This path attribute indicates that the local system selected a less specific route instead of a more specific route.

origin egp—(Optional) BGP origin attribute that indicates that the path information originated in another AS.

origin igp—(Optional) BGP origin attribute that indicates that the path information originated within the local AS.

origin incomplete—(Optional) BGP origin attribute that indicates that the path information was learned by some other means.

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.

Related Documentation