OSPF routing table

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Apr 19th, 2007
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What could possibly cause two routers to exchange only a partial OSPF routing table and not the entire routing?

Correct Answer by CSCO10899265 about 9 years 11 months ago

Hi,


this is entirely possible in a Frame relay NBMA scenrio where you are running OSPF as the routing protocol. apart from this incorectly configured neighbor commands and also rarely duplicate router id's could be the cause of this issue.


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Jon Marshall Thu, 04/19/2007 - 22:54
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Hi


Could you perhaps provide a few more details ie. the config of the 2 routers, the routing tables on each.


OSPF routers do not exchange routing tables with each other. They use LSA's between each other to build a link state database and then each routers derives it's own routing table from this database.


Jon

royalblues Thu, 04/19/2007 - 23:33
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Friend,


As jon said ospf does not advertise the routes to its neighbors.


you can certainly use distribute lists to stop routes entering the routing table


The distribute-list commands are supported in OSPF but work differently than distance-vector routing protocols such as Routing Information Protocol (RIP) and Enhanced Interior Gateway Routing Protocol (EIGRP). OSPF routes cannot be filtered from entering the OSPF database. The distribute-list in command only filters routes from entering the routing table; it does not prevent link-state packets from being propagated. Therefore, this command does not help conserve router memory, and it does not prohibit a router from propagating filtered routes to other routers


HTH, rate if it does

Narayan

Correct Answer
CSCO10899265 Sun, 04/22/2007 - 17:38
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Hi,


this is entirely possible in a Frame relay NBMA scenrio where you are running OSPF as the routing protocol. apart from this incorectly configured neighbor commands and also rarely duplicate router id's could be the cause of this issue.


ciologin Sun, 04/29/2007 - 18:49
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I checked my configuration and found out that I have a duplicated VLAN ID, I'm surprise how it could lead to this situation. Anyway thanks for every body, the hint of the duplicate router ids help me allot. Thank you

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