Description
This article describes how to filter static routes which will be redistributed to OSPF domain.
It approaches the problem step-by-step with problem explanation and final result verification.
Also, it illustrates how to change the metric type of the redistributed static route from default E2 to E1.
Solution
Starting status:
At the beginning of this example there are two static routes in the routing table:
cluster-a # get router info routing-table all
path=router, objname=info, tablename=(null), size=0
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default
S* 0.0.0.0/0 [10/0] via 192.168.196.254, port1
S 192.168.10.0/24 [10/0] is directly connected, port2
S 192.168.33.0/24 [10/0] is directly connected, port2
C 192.168.112.0/24 is directly connected, port2
C 192.168.196.0/24 is directly connected, port1
The objective is to distribute only 192.168.33.0/24.
The static routes are not distributed by default. In next step the redistribution will be enabled.
config redistribute "static"
set status enable
end
Both of them will now be redistributed.
cluster-a # get router info ospf database brief
path=router, objname=info, tablename=(null), size=0
Router Link States (Area 0.0.1.47)
Link ID ADV Router Age Seq# CkSum Flag Link count
0.0.3.2 0.0.3.2 103 80000004 0564 0031 1
AS External Link States
Link ID ADV Router Age Seq# CkSum Flag Route Tag
192.168.10.0 0.0.3.2 142 80000001 064a 0021 E2 192.168.10.0/24 0
192.168.33.0 0.0.3.2 142 80000001 0831 0021 E2 192.168.33.0/24 0
cluster-a #
This is not what is required. Three steps are needed to change the behavior.
- Prepare access-list.
- Prepare route-map using the access-list.
- Use the route-map.
Step 1: Prepare access-list.
config router access-list
edit "wanted-static-routes"
config rule
edit 1
set prefix 192.168.33.0/24
set exact-match enable
set action permit
next
end
end
end
Step 2: Prepare route-map using the access-list:
config router route-map
edit "static-to-ospf"
config rule
edit 1
set match-ip-address "wanted-static-routes"
next
end
end
end
Step 3: Use the route-map.
config router ospf
config redistribute "static"
set status enable
set routemap "static-to-ospf"
end
end
Verification of Configuration and Troubleshooting:
Now the behavior should be as expected.
cluster-a # get router info ospf database brief
path=router, objname=info, tablename=(null), size=0
Router Link States (Area 0.0.1.47)
Link ID ADV Router Age Seq# CkSum Flag Link count
0.0.3.2 0.0.3.2 9 80000006 0166 0021 1
AS External Link States
Link ID ADV Router Age Seq# CkSum Flag Route Tag
192.168.33.0 0.0.3.2 14 80000002 0632 0021 E2 192.168.33.0/24 0
As per the above output, OSPF shows the default Metric-Type 2 (E2) for redistributed static route 192.168.33.0/24.
To change the metric type from default E2 to E1 then run the below command.
config router ospf
config redistribute "static"
set status enable
set routemap "static-to-ospf"
set metric-type 1
end
end
Related Article:
Technical Note : How to control (filter) OSPF route redistribution with access-list and route-map
