Redistribution problem EIGRP -> OSPF

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Oct 12th, 2007
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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; 192.168.1.0/24 (this is the link between Meg and Peter), and 192.168.2.0/24 (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, 172.30.1.0 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, 192.168.1.0; which Lois is NOT at all directly connected to?


Thanks.


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Kevin Dorrell Fri, 10/12/2007 - 20:17
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redistribute eigrp 540 subnets


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


Kevin Dorrell

Luxembourg


CriscoSystems Mon, 10/15/2007 - 08:57
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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
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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
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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 172.30.0.0 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
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It will not redistribute the 172.30.0.0/16 prefix unless you actually have the 172.30.0.0/16 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

Luxembourg


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