Destination Gateway VLAN Type Sub-Type Metric Dist
----------- ------- ---- ---- -------- ------ ----
20.0.15.1/32 25.0.67.131 25 ospf external2 10 110
20.0.16.2/32 25.0.67.131 25 ospf intra-area 2 110
Configuring external route redistribution in an OSPF
domain (optional)
For more information, see
Configuring for external route redistribution in an OSPF domain
on page 259.
Configuring redistribution filters
Syntax:
router ospf restrict
ip-addr/mask-length
Prevents distribution of the specified range of external routes through an ASBR from sources external to the
OSPF domain. This will prevent external routes with the specified IP address/mask from entering the OSPF
domain.
NOTE:
This command can be used to help implement inbound traffic filtering.
Default: Allow all supported, external route sources.
NOTE:
Use this command to block unwanted, external routes before enabling route redistribution on
the ASBR.
Example:
To configure a routing switch operating as an ASBR to filter out redistribution of static, connected, or RIP routes
on network 10.0.0.0, enter the following commands:
switch(config)# router ospf restrict 10.0.0.0/8
NOTE:
In the default configuration, redistribution is permitted for all routes from supported sources.
Enabling route redistribution
This step enables ASBR operation on a routing switch, and must be executed on each routing switch connected
to external routes you want to redistribute in your OSPF domain.
The basic form of the
redistribute
command redistributes all routes of the selected type. For finer control over
route selection and modification of route properties, you can specify the
route-map
parameter and the name of
a route map. (For general information on route policy and route maps, see
. For examples of using
route maps in route redistribution, see
Using route policy in route redistribution
NOTE:
Do not enable redistribution until you have configured the redistribution "restrict" filters.
Otherwise, the network might become overloaded with routes that you did not intend to redistribute.
Syntax:
[no] router ospf redistribute [connected | static | rip] route-map
name
Executed on an ASBR to globally enable redistribution of the specified route type to the OSPF domain through
the area in which the ASBR resides.
Chapter 11 Open Shortest Path First Protocol (OSPF)
205
