Hi,
Route maps are used for a lot of different purposes in IOS. In the context of routing, consider two particular uses of it:
- when redistributing routes from one protocol to another
- when advertising/receiving routes via BGP
Both of the above applications provide advanced filtering capabilities. The traditional method of filtering was via the use of access-lists. This, however, limits you to just matching on the prefix and prefix length. With route-maps, you have the ability to match on things such as metrics, BGP attributes (communities, AS-PATH), outgoing interface, source of the routing update etc. Based on the matches, you can either decide to permit or deny the route.
Additionaly, with a single route-map, you can specify multiple different clauses so that you can apply different actions to different sets of routes.
Hope that helps - pls rate the post if it does.
Paresh
