ahmet-saat Sat, 03/31/2007 - 08:36
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We use virtual link where some areas have not a direct connection to the backbone area (Area 0). So here in what you sent, area 2 does not have a connection to Area 0, so virtual-link is necessary.

Router 3 has not a direct connection to Area 0 actually, but It thinks that it has a direct connection to Area 0 through Virtual links. All communication between Router 1 and Router is tunneled through virtual link thats why u see that is indicated "0" in the Router 3's routing table.

pls rate if it helps.

ganpatspatil Sun, 04/01/2007 - 03:45
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Thanks ...let me know how r1 showing as "OIA",this is also show as "O" as r3 is directly connected to R1 over virtual link...

O IA [110/75] via, 00:38:02, Serial2/1/0

rajinikanth Sat, 03/31/2007 - 11:29
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OSPF requires that all areas be connected to area 0 and that area 0

must be contiguous. When this is not possible, you can use a virtual

link to bridge across an intermediate area.

Verify that the virtual link is up with the show ip ospf virtual-links

command. Additionally, virtual interfaces are treated as actual interfaces

by the OSPF process, and thus, their status can be verified with the

show ip ospf interface interface-id command.



sundar.palaniappan Sun, 04/01/2007 - 05:29
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In your setup all 3 routers are ABRs;

R1 is part of area 1 & 0

R2 is part of area 1 & 0

R3 is part of area 1, 2 & 0 is part of area 2 and therefore it's an 'OIA' (inter-area) route as neither R1 or R2 are part of area 2.




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