how do i solve this ?

How do i solve this problem?

I am sending a summary address of on both interfaces on r3 and r4 to the grey stub sites. i am protecting to sending that summary back into eigrp 1 on the same routers by blocking it in a route-map when redistributing back as i dont want transit traffic to go through the stub sites.

That works fine. But what if another router in eigrp 10 decides to redistribute a static default route. Say r6. I can match on a interface, s1/0 on r3 and r4 for sure, and that works, allowing the default from r6 on to r5, but the summary's on r3 and r4 point to null causing mayhem/loop when i trace from r5 to the loopback on r6.

I remember there is a command (at least in OSPF, discard-route?) to not install the summary to null, but i am not sure it's wise to remove it? 

Sorry you can't see R5 in this picture, it's to the right where R3 and R4 meet.




  • Can you clarify what is the issue here and what do you want to accomplish here ?

  • Well as i said, i dont want the summary i send on the s1/0 interface towards eigrp 10 to appear in eigrp 1, so

    i block it in a route-map. I do however want the summary from R6. 


    While this works (i get the summary from r6 on r5) i get a loop when tracing that route because both r3 and r4 discard that route as i originate summary's on the s1/0 interface for the other summary which installs a summary route to null.

    Does that make sense?

  • Try setting the AD of the summary route to 255. That should keep it from being installed in RIB. I'm not saying it's a good design but just try it to see if that resolves the loop.

  • Hey Daniel,

    Yeah i tried that, but then it only sends in one summary-route. I get weird results then.

    Thanks though.

  • Try to do these steps

    1. On R3 and R4, remore NULL0 route from the routing table by changing the AD value to 255

    2. On R3 and R4, links connected to EIGRP AS10 block default route coming back to them using distrubute list

    3. Default route from R6 is external route, will install in the routing table of R3 and R4 and hence redistributed to EIGRP AS1.

    4. Keep metric value lower (for default route originated at R6) on R4 which redistributing from AS10 to AS1.

    This way traffic from R5 will follow from R5 -->R4--->R6

  • But now the spoke routers will install that external route instead of the summary-route instead.

    I suppose i could fix it by blocking incoming default routes.

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