2 Replies Latest reply: Mar 9, 2012 4:09 AM by Jonny7_2002 RSS

    Routing Table


      Hi CLN


      I have the following doubts:


      1. What order does the routing table processes destination based routing? is it the longest prefix first and lowest AD next or vice versa??

          I got some really confusing results in my lab


      2. If OSPF summarization is to be done at a specific area with two ABRs then should we do the summarization in both the routers or does OSPF has a feature for propagating summary routes between ABRs



      Can someone please clarify??





        • 1. Re: Routing Table



          1) longest prefix match and AD is only for installing prefixes of equal lengths that were learned by 2 different sources.

          2) you can do on both or on one only and no the summary is not propagated between ABRs but of course the other ABR knows about the summary as it is part of the area where the summary is injected.





          • 2. Re: Routing Table

            1. If you had the following two routes in the table:....



            If a packet then hit the router with a destination of then entry B. above ( would be used as it has a more specific prefix.


            2. If you were summarising from one router, you would want to summarise from the other aswell other wise one router will advertise the summary route and the other will advertise the more specific routes which would be pointless. it would possibly stop utilisation of one router in favor of the other due to the more specific routes aswell.


            Hope this helps