Route maps provide a means to both filter and/or apply actions to route, hence allowing policy to be applied to routes.
|• Route Map Command:|
|• Route Map Match Command:|
|• Route Map Set Command:|
|• Route Map Call Command:|
|• Route Map Exit Action Command:|
|• Route Map Examples:|
Route-maps are an ordered list of route-map entries. Each entry may specify up to four distincts sets of clauses:
This specifies the policy implied if the ‘Matching Conditions’ are met or not met, and which actions of the route-map are to be taken, if any. The two possibilities are:
The ‘Matching Policy’ is specified as part of the command which defines the ordered entry in the route-map. See below.
A route-map entry may, optionally, specify one or more conditions which must be matched if the entry is to be considered further, as governed by the Match Policy. If a route-map entry does not explicitely specify any matching conditions, then it always matches.
A route-map entry may, optionally, specify one or more ‘Set Actions’ to set or modify attributes of the route.
Call to another route-map, after any ‘Set Actions’ have been carried out. If the route-map called returns ‘deny’ then processing of the route-map finishes and the route is denied, regardless of the ‘Matching Policy’ or the ‘Exit Policy’. If the called route-map returns ‘permit’, then ‘Matching Policy’ and ‘Exit Policy’ govern further behaviour, as normal.
An entry may, optionally, specify an alternative ‘Exit Policy’ to take if the entry matched, rather than the normal policy of exiting the route-map and permitting the route. The two possibilities are:
The default action of a route-map, if no entries match, is to deny. I.e. a route-map essentially has as its last entry an empty ‘deny’ entry, which matches all routes. To change this behaviour, one must specify an empty ‘permit’ entry as the last entry in the route-map.
To summarise the above: