2.6 Default Routing - to go along with my 2.5 solution

So with my solution in 2.5 I can make a alternate solution to 2.6 with the fact that I know that R1 and SW2 can not accept routes that have be redistributed from EIGRP.

2.6 Default Routing

  • Configure R3 to originate a default route into the OSPF domain.
  • This route should be withdrawn if R3 loses its connections to both R1 and R2.
  • Do not configure any other device but R3 to accomplish this.
  • Use the minimum number of commands possible.

My soltuion for 2.6

ip prefix-list R2-LOOPBACK-PL seq 5 permit

route-map R1-R2-CHECK-MAP permit 10
 match ip address prefix-list R2-LOOPBACK-PL

router ospf 1
 default-information originate route-map R1-R2-CHECK-MAP

My solution only adds 4 lines where the SG adds 6 new lines.



  • Well sleeping on this over night I got to thinking that if we orginate a default route on R3 it should loop around to SW2 and get redistributed into EIGRP.  This would flood the whole network with a default route.

    I though that there would be something that against this but after re-reading the question and the SG solution I'm pretty sure that both the SG solution and mine would allow the default route to be flooded.

    This would create a very big routing loop for any traffic that is not known in the network and would only die when the TTL expired.

    Since I'm not 100% sure of this I'm going to remove my solution and use the books solution to see if they have the same problem.

    If you have done this lab or are doing this lab - what are you thought on the default route loop?

    R3 (OSPF default orginate) =>R4 => SW1 => SW4 => SW2 (OSPF to EIGRP) => R1 => R3


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