Problem with OSPF External Routes - Packet Tracer

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May 1st, 2012
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i created a network in Packet Tracer, so that the various OSPF-Area Types can be used and tested.

There is also a NSSA-Area (which also could be converted into a usual area) with an ASBR (BGP).

When i look at the routing of a router not in the same area table i do not find the external route.

Also the ASBR does not receive any summary like in a stub area on the same network where it works as proposed.

To evaluate this problem i provide the network Packet-Tracer file.

Be sure to let some time for ospf to converge.

After some time Router4 shows a expected routing table, containing all ospf routes and one external nssa-route.

But looking at Router9 the routing-table shows some ospf-routes but not all and not a default-route as i would epxect with no-summary.

And looking at Router3 there are all ospf-routes but no external ones...

But in the ospf database at Router3 the ASBR is not unknown, so the Router4 does announce the ASBR.

But it should also propagate external routes into area 0.

Can someone help me with that?

Perhaps it is some ospf understanding problem or packet tracer problem...


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Overall Rating: 5 (1 ratings)
Sebastian Kricner Tue, 05/01/2012 - 15:18
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I have found a hint, that Packet Tracer probably does not support LSA 5 for redistributed Networks.

Page 111

But interestingly "show ip ospf database" shows the LSA 5 propagation. So then a implementation for its support in my oppinion should not be that difficult...

But i may switch to GNS3 as already in some cases done because of lack of other things, like FHRP.

And combining that with real hardware...but on the other hand not everyone uses up to date computers with plenty of RAM

Sebastian Kricner Fri, 05/11/2012 - 10:39
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I have solved this issue.

The problem was that using nssa no-summary, that no summaries get sent into a nssa area by the other ABR.

So the ASBR in the nssa could not get the networks needed for routing.

no-summary is useful if the EGP ist running on a ABR.

Sebastian Kricner Fri, 05/11/2012 - 10:49
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Ok, i was refering to a other simulation in nearly same design and somewhat other problem.

Seems the issue described in the topic still persists, even with nssa.

Sorry for the brabble in the last posts.


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