Thursday, December 17, 2015

Stop Originating Type 7 LSAs Only in ASBABRs

Let me explain the topic. In the diagram, you can clearly see that the R2 is the ABR. But in this lab it is also the ASBR.


It is redistributing its connected subnet of the loopback 0 to the both area 1 (the NSSA) and area 0. When you enter the redistribute command it will start redistributing to both sides. As LSA type 7 to the NSSA and as LSA type 5 to the area 0.

If you do not want the routers of the NSSA to learn the redistributed routes while only the backbone routers to learn the routes, here is the way to do it.

Configuration files can be downloaded from here.

Let's see the databases of R3 & R1 1st.

We can see the redistributed route is advertised to both areas. To stop it goes to the NSSA just enter the following command in OSPF configuration of R2 which does the redistribution.

R2(config)#router ospf 1
R2(config-router)#area 1 nssa no-redistribution

You can see the databases again to see the effect. LSA type 7 is no longer in the NSSA.

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