Task: 6.38 WB-1 OSPF Summarization and Discard Routes

Hi guys,

Task:  " • Ensure that R5, SW2, and SW4 can still reach the Loopback 0 networks of
R1 and R2, even with the previously configured distribute-list filter applied."

I need someone to confirm that R2 lo0 won't be reachable after the "no discard-route internal" command is invoked @ R5. And only R1 lo0 is reachable.






  • Yes, it will work since the discard-route is removed and it is matched with the default route for the destination. Even though particular prefix is filtered with the distribute-list, there is a summary route exist on Sw2 which forwards the traffic destined to R1 & R2's loopbacks. Then, R5 forwards the traffic based on the default route as there is no discard-route exists once you disable it.


  • hmm, but R4 is using R5 as a next hop for R2's lo0, right? because I'm getting a loop between R4 & R5 when tracing lo0 of R2 from SW2 or R5.
    R5 is using the candidate default route towards R4 because there is no specific route to the since the "no discard route internal" is executed- . and at the same time R4 is using a route learned from R5 to reach R2's lo0. This is what I'm getting in my lab.

    So, from R5 or area 3, R1 lo0 will be reachable but not R2's lo0

    Am I right?

  • Please check the routing table of R4, you should have R2's loopback network in order to have the reachablity. You might be missing something in routing portion. At first, check for the routing table of R4 , R1 then R3 & post the result.

    Good luck!

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