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External (Type 5) Route Summarization in OSPF

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  • 1.  External (Type 5) Route Summarization in OSPF

    Posted 09-28-2012 11:29

    I am trying to find a way to summarize routes "redistributed" from another IGP, say RIP, into OSPF.

     

    For example, if I had an ASBR in Area 0 redistributing 100.100.0.0/24, 100.100.1.0/24, 100.100.2.0/24 and 100.100.3.0/24 from RIP to OSPF, I only want to advertise the 100.100.0.0/22 Type-5 LSA into the backbone.

     

    This is possible in IOS with the use of the "summary-address" command.

     

    So far as I can tell, Junos only does summarization at ABRs using "area-range" or "nssa area-range" commands.

     

    Is this even possible in Junos, to do this on the ASBR itself?

     

    Thanks,

     

    Nic


    #ospf
    #iostojunos
    #summarization


  • 2.  RE: External (Type 5) Route Summarization in OSPF
    Best Answer

    Posted 09-28-2012 12:05
    good question.
    I also struggled with this one some time back. Here is an excellent blog entry that explains it:

    http://noshut.blogspot.in/2012/03/ospf-external-route-summarization.html


    HTH
    #ASBR
    #ospf
    #lsa
    #summarization


  • 3.  RE: External (Type 5) Route Summarization in OSPF

    Posted 09-28-2012 12:35

    Thanks, that was helpful.

     

    The salient points that I carried away are as follows, can someone verify -

     

    1. No specific IOS equivalent "summary-address" command

    2. Create an aggregate/generated route covering the desired routes

    3. Instead of importing the IGP routes in the routing policy, import the aggregate/generated route

     

    Would this workflow be the only possible way or does someone have a more streamlined flow?

     

    Thank again,

     

    Nic


    #ospf
    #iostojunos
    #summarization


  • 4.  RE: External (Type 5) Route Summarization in OSPF

    Posted 09-29-2012 02:10

    As of my understanding you are correct. 



  • 5.  RE: External (Type 5) Route Summarization in OSPF

    Posted 09-29-2012 08:18
    yes, you're right. There is no single command that will summarize OSPF external routes on the ASBR.
    The workaround mentioned on that blog post works fine though.


  • 6.  RE: External (Type 5) Route Summarization in OSPF

    Posted 06-23-2013 12:48

    You could convert the area to nssa and then apply area-range command under the nssa stanza on the ABR, that will summerize external routes.