3

I have Area 0 and Area 1, Area 1 is configured as NSSA and there is this router R3 in this area that works as ASBR and redistributing/injecting some external routes from some other routing domain into Area 1, I know Type 7 LSA allows injection of external routes through Not-so-Stubby-Areas (NSSA), and I know since type 5 LSA are not allowed inside any stub area, Type 7 LSA is used, to trick OSPF. Type 7 LSA is generated by NSSA ASBR and is translated into type 5 LSA as it leaves the area by NSSA ABR, which is then propagated throughout the network as type 5 LSA, so please do not state the obvious.

The question is:

Is it possible to summarize routes that come from other routing domain through NSSA ASBR in mentioned scenario?

For example I got these static routes on my NSSA ASBR and I want to summarize them:

192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
192.168.4.0/24
192.168.5.0/24
192.168.6.0/24

I want to summarize them to one single route like 192.168.0.0/21, and then inject them to ospf routing domain, through NSSA ASBR, is that possible to do on a Cisco router?

I've already tried summary-address command on NSSA ASBR, but it didn't work.

thank you

  • Oh thanks for editing my post,actually I did my best,to have this post come out this way but I don't know how it scrambled and got out of order. – Mjaryan May 18 '14 at 21:39
  • It should work. Can you post your config? – Ron Trunk May 19 '14 at 19:17
  • This question was asked and answered on learningnetwork.cisco.com/thread/70826 – Ron Trunk Jul 14 '14 at 0:36
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 8 '17 at 21:26
3

I would suggest creating a static route to Null 0 on the external router:

ip route 192.168.0.0 255.255.248.0 Null 0

  • Static route to Null interface is seen as a connected interface on the local router.

    Then advertise the summary address in whatever routing protocol is originating the routes with a network statement in the routing process.

When you redistribute from one routing process to the other the summary route should be injected into the OSPF process.

You could also filter out the subnets with a prefix list or route map to be sure the smaller subnets don't get injected.

Hopefully this helps.

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