User Manual

Enterasys X-Pedition User Reference Manual 241
Route Import and Export Policy Overview
In some cases, a combination of the associated attributes can be specified to identify the routes to
be exported.
Route-Filter
This component specifies the individual routes which are to exported or restricted. The metric to be
associated with these routes can also be explicitly specified using this component.
The metric associated with the exported routes are inherited unless explicitly specified. If there is
no metric specified with a route-filter, then the metric is inherited from the one specified with the
export-source.
If a metric was not explicitly specified with both the route-filter and the export-source, then it is
inherited from the one specified with the export-destination.
Every protocol (RIP, OSPF, and BGP) has a configurable parameter that specifies the default-
metric associated with routes exported to that protocol. If a metric is not explicitly specified with
the route-filter, export-source as well as export-destination, then it is inherited from the default-
metric associated with the protocol to which the routes are being exported.
Specifying a Route Filter
Routes are filtered by specifying a route-filter that will match a certain set of routes by destination,
or by destination and mask. Among other places, route filters are used with martians and in import
and export policies.
The action taken when no match is found is dependent on the context. For instance, a route that
does match any of the route-filters associated with the specified import or export policies is
rejected.
A route will match the most specific filter that applies. Specifying more than one filter with the
same destination, mask, and modifiers generates an error.
There are three possible formats for a route filter. Not all of these formats are available in all places.
In most cases, it is possible to associate additional options with a filter. For example, while creating
a martian, it is possible to specify the allow option, while creating an import policy, one can specify
a preference, and while creating an export policy one can specify a metric.
The three forms of a route-filter are:
• Network [exact | refines | between number,number]
• Network/mask [exact | refines | between number,number]
• Network/masklen [exact | refines | between number,number]
Matching usually requires both an address and a mask, although the mask is implied in the
shorthand forms listed below. These three forms vary in how the mask is specified. In the first form,