Description

This article provides information on how to configure the network summary LSA to reject inter area routes.

Symptoms

Two routers ( SRX_A and SRX_B ) are being used. SRX_A  is present in both area 0 and area 1 , whereas SRX_B is present only in area 1 . The 2.2.2.0/30 internal route is present in area 0 , which area 1 should not able to view.

Solution


Without restricting the routes, the routing-table on  SRX_B contains the 2.2.2.0/30 route as follows: 

root@SRX_B# run show route    

inet.0: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.0/30         *[Direct/0] 00:06:58
                    > via fe-0/0/0.0
1.1.1.2/32         *[Local/0] 00:08:50
                      Local via fe-0/0/0.0
2.2.2.0/30         *[OSPF/10] 00:00:21, metric 2
                    > to 1.1.1.1 via fe-0/0/0.0
224.0.0.5/32       *[OSPF/10] 00:08:53, metric 1
                      MultiRecv
An export policy is created on  SRX_A to restrict the export of 2.2.2.0/30 : 
[edit]
root@SRX_A# show policy-options 
policy-statement p1 {
    term t1 {
        from {
            route-filter 2.2.2.0/30 exact;
        }
        then reject;
    }
    term t2 {
        then reject;
    }
}
Now, apply this policy as the network-summary-export policy in area 1 as follows: 
[edit]
root@SRX_A# set protocols ospf area 1 network-summary-export p1
root@SRX_A# commit
commit complete
Verification :

The route table on SRX_B is as follows: 
[edit]
root@100-2# run show route            

inet.0: 3 destinations, 3 routes (3 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.0/30         *[Direct/0] 00:07:48
                    > via fe-0/0/0.0
1.1.1.2/32         *[Local/0] 00:09:40
                      Local via fe-0/0/0.0
224.0.0.5/32       *[OSPF/10] 00:09:43, metric 1
                      MultiRecv