Route Map Overview
A route map is a set
of statements that the device applies in sequential order to a route.
Each statement in the route map defines a condition that is compared
to the route. A route is compared to each statement in a specified
route map in order of increasing sequence number until there is a
match, then the action specified by the statement is applied. If the
route matches the condition in the route map statement, the route
is either permitted or rejected.
A route map statement can also modify certain attributes
of a matching route. There is an implicit deny at the end of every
route map; that is, if a route does not match any entry in the route
map, the route is rejected.
For each match condition, you specify whether a
route that matches the condition is accepted (permitted) or rejected
(denied). If a route matches a condition and is permitted, you can
optionally set attribute values for the route. You can configure additional
entries for the same route map, specifying a different sequence number
for each entry.
Route Map Match Conditions
The match conditions that can be configured for
a route map are displayed in Table 1.
Table 1: Route MAP Match Conditions
Property
|
Description
|
AS Path (BGP)
|
Select the AS path access list a route must match.
|
Community (BGP)
|
Select the community a route must match.
|
Metric
|
Select the route metric a route must match.
|
Interface
|
Select the interfaces a route must match.
|
Access List
|
Select the access list a route must match.
|
Next-Hop
|
Match a specified access list. It also supports IPv6,
from ScreenOS 6.3.
|
Route Type (OSPF)
|
Select the route types (OSPF internal, external type
1, or external type 2) that a route must match.
|
Tag
|
Select the route tag value a route must match.
|
Permitted Route Attributes
The attributes that be configured for matching
permitted routes are displayed in Table 2.
Table 2: Permitted Route Attributes
Property
|
Description
|
AS Path (BGP)
|
Prepends a specified AS path access list to the path
list attribute of the matching route.
|
Community (BGP)
|
Sets the community attribute of the matching route to
the specified community list.
|
Next-Hop
|
Sets the next-hop of the matching route to the specified
IP address.
|
Tag
|
Sets the tag of the matching route to the specified tag
value or IP address.
|
Weight
|
Sets the weight of the matching route.
|
Metric Type (OSPF)
|
Sets the OSPF metric type of the matching route to either
external type 1 or external type 2.
|
Local Preference (BGP)
|
Sets the local-pref attribute of the matching route to
the specified value.
|
Preserve
preference (ScreenOS 5.1 and later only)
|
Preserves the preference value of the matching route
that is exported into another virtual router.
|
Metric
|
Configures how the virtual router assigns a metric to
permitted routes (select one):
- Use Metric Specified By User as Imported/Exported Route
Metric—When enabled, the VR assigns the specified metric value
to all matching routes.
- Use the Source Route Metric as the Imported/Exported Route
Metric—When enabled, the VR preserves the metric of a matching
route that is imported or exported into another virtual router.
- Offset Metric
(ScreenOS 5.1 and higher only)—When enabled, the VR increments
the metric of the matching route by the specified number. Use this
option to increase the metric on a less desirable path. For RIP routes,
you can apply the increment to either routes advertised (route-map
out) or routes learned (route-map in). For other routes, you can apply
the increment to routes that are exported into another virtual router.
|
For instructions on configuring virtual router
route maps, see the Network and Security Manager Online
Help.
Published: 2009-08-23
