OSPF routes are not installed in the routing table.

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Aug 14th, 2008
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Has anyone heard about the situation when OSPF does not install routes in the routing table on both side of a link, even though adjacency forms fine

and the database is populated?

I only have the config from one side of the link at the moment. The connection is over ADSL, the interfaces on both sides are numbered.

Any ideas anyone?

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Richard Burts Thu, 08/14/2008 - 03:20
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There are several things that could produce the symptoms that you describe. If a distribute list were configured it would allow entries in the link state data base but not allow the entries in the routing table. If they were external routes and the forward to address were not reachable the entries would be in the link state data base but not in the routing table. If the prefix were learned from something with a better administrative distance it would not put the OSPF route into the routing table.

It would help us understand the issue if you would post the router config that you do have. Also it would help if you would post the output of show ip route and of show ip ospf data showing the entries in question that do not get into the routing table.



vaisharm Thu, 08/14/2008 - 03:26
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Hi Victor,

The most common possible causes of this problem are:

- The network type is mismatched.

- IP addresses are flipped in dual serial-connected routers or a subnet/mask mismatch has occurred.

- A distribute list is blocking the routes' installation.

- The routes are learned from another IGP with a better metric.

The configuration, show ip route, show ip ospf database, show ip ospf nei and show ip ospf interface from the two routers would be helpful.


vaisharm Thu, 08/14/2008 - 03:29
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Looks like Rick had already replied. Need to type faster I guess ;)


Giuseppe Larosa Thu, 08/14/2008 - 11:17
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Hello Victor,

the simplest reason for this could be the presence of one or more static routes with a better AD that have been used before setting up the OSPF protocol.

All other cases are described in Rick's post.

If it is not so simple as I suppose it is post the sh ip route, sh ip ospf database and the sh ip interface for the ADSL link.

be aware that using an ATM point-to-point subif or using the main ATM interface can lead to two different OSPF network type.

There was a similar case some weeks ago where the problem was the OSPF network type mismatch at the two ends of the ATM link.

Hope to help



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