OSPF configuration

Unanswered Question
May 29th, 2007
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Here is a sample net diagram-


R3 (s1/0) - R5 (s1/0) - R4 (s1/0)

----------- R5 (e0/1) - R4 (e0/0)


I have Frame Relay running using the serial connections in R3, R5, and R4 and OSPF is enabled with AS 0.


I also have a Ethernet connection between R4 and R5 that configured with OSPF AS 45.


OSPF is working just fine thru the serial connections on top of Frame Relay. For the Ethernet connections I am using OSPF Non-broadcast and only works when I specify from R4 "neighbor (R5's e0/1 ip address) (that I found in a sample configuration). My question is what is the purpose of the Neighbor command in OSPF?


Thank you.




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Richard Burts Tue, 05/29/2007 - 10:12
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The neighbor command is used in OSPF in nonbroadcast environments. In a nonbroadcast environment OSPF can not be sure that its HELLO packets will discover neighbors (since HELLO packets are multicast and multicast may not work in nonbroadcast environments). So if you tell OSPF that a certain interface is non-broadcast then OSPF does not depend on multicast HELLO to discover neighbors and does depend on you to manually configure the neighbor relationship.


I am not clear why you configure the Ethernet (clearly a broadcast media) as non-broadcast. But when you do configure this then the neighbor command is needed.


HTH


Rick

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