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OSPF: Configuring Route Maps for Filtering and Modifying OSPF Routes
Page 50 | Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes
OSPF: Configuring Route Maps for Filtering and
Modifying OSPF Routes
For information about route maps and their structure, see "Structure of a route map" on
page 26.
Route maps can be applied to OSPF routes as well as BGP routes. Of course, the route
maps that can be used with OSPF are rather limited in comparison with those that are used
with BGP, as OSPF route updates do not carry attributes in the way that BGP route updates
do.
Also, OSPF route maps can only be applied to importing:
OSPF-learnt routes into the main IP route table, or
static, BGP or RIP routes into OSPF
Filtering cannot:
remove an entry from the LSA database once the entry has been added
prevent the router from advertising an LSA database entry to interfaces in the same area
that the entry is relevant to
prevent updates that OSPF learns from being put into the LSA database
change the properties of an entry in the LSA database
This is because OSPF shares LSAs between all the routers in an area. The protocol assumes
that all the routers in the area have shared all the advertisements among each other, and that
all agree on the state of the complete link state database for the area. If some routers in the
area are learning, but not advertising, that breaks the OSPF model.
Configuring a match clause
A match clause can match on the following criteria.
Note: When configuring a match clause, make sure you are in route map mode.
The prompt should look like: awplus(config-route-map)#
Metric
The entry will match all routes whose metric is equal to that specified in the clause.
To match a metric value, use the command:
match metric <value>
Interface
The entry will match all routes learnt via the specified VLAN.
To match a VLAN, use the command:
match interface <vlan>