OSPF E2 type route

Answered Question

I am a bit confused with the ospf type E2 route. As per the doc when a route is marked as type E2, it does not calculate the metric to the ASBR

Then referring to the attached diagram, why isn't that iam seeing 2 routes for the subnet 1.1.1.0/24 and the drfault 0.0.0.0

R2 and R4 have been configured with default-information originate command

At R3 I see only one default route from R2.

Ambi

Attachment: 
I have this problem too.
0 votes
Correct Answer by Edison Ortiz about 8 years 9 months ago

Ambi,

What you are seeing is called recursive-routing. In order for R3 to know about routes from R4, the cost is 2 from R3 (see show ip route)

O 20.20.20.4 [110/2] via 30.30.30.2

while in order for R3 to know about routes from R2, the cost is 1 - the cost of the fastethernet interface.

Increasing the cost on the fastethernet interface on R3 that is facing R2 (ip ospf cost 2) should provide the desired result.

HTH,

__

Edison.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (3 ratings)
Loading.
Correct Answer
Edison Ortiz Sun, 02/10/2008 - 09:16

Ambi,

What you are seeing is called recursive-routing. In order for R3 to know about routes from R4, the cost is 2 from R3 (see show ip route)

O 20.20.20.4 [110/2] via 30.30.30.2

while in order for R3 to know about routes from R2, the cost is 1 - the cost of the fastethernet interface.

Increasing the cost on the fastethernet interface on R3 that is facing R2 (ip ospf cost 2) should provide the desired result.

HTH,

__

Edison.

Edison Ortiz Sun, 02/10/2008 - 09:54

> Increasing the cost on the fastethernet interface on R3 that is facing R2 (ip ospf cost 2) should provide the desired

> result.

Looking back, I'm not 100% sure about this statement as R3 sees R2 via connected so OSPF does not play a part of the cost here. Please test and let me know.

__

Edison.

royalblues Mon, 02/11/2008 - 00:04

Edison is absolutely correct that the behavior is due to recursive routing.

I managed to lab the setup and it works

you should see the two routes in the rotuing table as required if you increase the ospf cost to 2 between R2 and R3

HTH

Narayan

Actions

This Discussion