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set as-path
Adds an autonomous system path set clause to the route map.
Syntax: [no] set as-path {tag | prepend as-path-string}
tag
For redistributing routes into BGP: converts the tag of a route into an autonomous system path.
prepend as-path-string
Prepends the as-path-string to the autonomous system path of the route that is matched by the route map.
Description: Use the set as-path tag command to convert the route tag of a redistributed route into an autonomous system path. This conversion modifies the autonomous system path length.
Use the set as-path prepend command to prepend the as-path-string onto BGP redistributed routes. Normal practice is to prepend the local autonomous system number multiple times to increase the autonomous system path length.
Use the no set as-path command to not modify the autonomous system path.
Route maps consist of sets of match and set commands. Match commands define the criteria for matching routes. Set commands define the actions applied to a route when it matches all criteria defined by the match commands.
Use the route-map command to create a route map. Use the various match and set commands to define the conditions for redistributing routes between protocols or between instances of the same protocol.
Autonomous system path length is the only global BGP metric that you can use to influence best-path selection. A BGP speaker can influence the best path selection by a peer by varying the length of the autonomous system path.
If you do not set local preference or weight, autonomous system path length determines which of multiple routes are selected. Routes with longer autonomous system paths are preferred. To prefer a path, you can pad the autonomous system path by prepending extra autonomous system numbers.
Factory Default: Autonomous system path is not modified.
Command Mode: Route map configuration.
Example: In the following example, routes with the tag value of 5 that pass the route-map are redistributed with an autonomous system path beginning with 120 120:
- The route-map command creates a route map named setfromtag.
- The match tag command adds a match clause to match routes with a route tag of 5.
- The set as-path prepend command specifies that routes that pass the match clause have 120 120 prepended to their autonomous system path.
- The router bgp command enables BGP and assigns the router to autonomous system 120.
- The redistribute command applies the route-map setfromtag to OSPF routes redistributed into BGP:
router(config)#route-map setfromtag permit 10
router(config-route-map)#match tag 5
router(config-route-map)#set as-path prepend 120 120
router(config-route-map)#end
router(config)#router bgp 120
router(config-router)#redistribute ospf 101 route-map setfromtag
The routes are redistributed into BGP with a modified autonomous system path.
Related Commands: route-map
match as-path
match community
match ip address
match ip next-hop
match ip route-source
match metric
show route-map
match route-type
match tag
set community
set community
set ip next-hop
set level
set local-preference
set metric
set metric-type
set origin
set tag
set weight
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Copyright © 2004
Avici Systems Inc.
Avici® and TSR®
is a registered trademark of Avici Systems Inc.
IPriori™, Composite Links™, SSR™, QSR, and NSR® are
trademarks of Avici Systems Inc.
Source
File Name: Routing_Pol.fm
HTML File Name: Routing_Pol32.html
Last Updated: 05/10/04 at 16:38:37