Redistribution problem EIGRP -> OSPF

Unanswered Question
Oct 12th, 2007
User Badges:
  • Bronze, 100 points or more

I have an AS 540 with four routers Frances is connected to Meg; Meg to Peter, Peter to Lois.

Lois also participates in AS 790 which runs OSPF. Lois's OSPF neighbors are Carter and Chris.

In Lois's OSPF process, I entered "redistribute eigrp 540."

Then I logged on to Chris and saw two E2 OSPF routes in his RT; (this is the link between Meg and Peter), and (the link between Peter and Lois).

But in Chris's routing table, I'm not seeing the loopbacks I configured on Frances: 24-bit loopbacks, thru 3.0, and these DO appear in Lois's routing table as EIGRP routes.

If they are in Lois's EIGRP routing table, and Lois is configured to redistribute EIGRP into OSPF, why are those routes not being advertised to Chris?

Especially when Lois IS advertising the Meg-Peter link,; which Lois is NOT at all directly connected to?


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Kevin Dorrell Fri, 10/12/2007 - 20:17
User Badges:
  • Green, 3000 points or more

redistribute eigrp 540 subnets

It should have given you a warning when you entered the command without the subnets.

Kevin Dorrell


CriscoSystems Mon, 10/15/2007 - 08:57
User Badges:
  • Bronze, 100 points or more

Except, shouldn't I have nonetheless seen the classful network 172.30 in Chris's routing table?

I did not.

e-dennington Mon, 10/15/2007 - 12:46
User Badges:

The classful network boundary for 172.30.x.x is /16 not /24 (it is a class B network) so you won't see the loopback addresses redistributed unless you use the subnets keyword in the redistribution statement under ospf.

CriscoSystems Mon, 10/15/2007 - 12:56
User Badges:
  • Bronze, 100 points or more

Yeah I know it's a 16-bit mask. Perhaps I should have made this clearer: There is NOTHING with the 172.30/16 prefix being redistributed into OSPF. Not even the classful network.

Or does the fact that I have the Lois router's EIGRP process configured with no auto-summary mean that unsummarized subnets will be dropped, rather than at least summarized for redistribution's sake?

I don't think that's fair to the nice redistribution process.

Kevin Dorrell Tue, 10/16/2007 - 05:43
User Badges:
  • Green, 3000 points or more

It will not redistribute the prefix unless you actually have the prefix in the topology database of the EIGRP. And it will not redistribute its subnets unless you have the subnets keyword.

I knows its a strange design decision, seeing as OSPF is VLSM aware. I guess it's OSPF's quirk, just like auto-summary is to RIP and EIGRP. (But rather different behavior, before anyone tries to correct me on that.) But at least it warns you.

Kevin Dorrell



This Discussion