Task 3.3 Virtual Link Question

Just wondering here. I agree with the solution for Task 3.3, but the explanation leaves me scratching my head. It says in the SG that the VL over Area 45 is there in case the frame-relay link between R4 and R3 goes down. Isn't the VL between R4 and R5 required so area 48 isn't segmented? Thanks in advance.


  • Hi bentleym,

    Area 45 will always be connected to area 0. The problem is if R4 looses the frame-relay connection S0/0 then Area 4 and Area 44 are not adjacent to an area 0.

    Once an area is not next to area 0 you loose connectivity. In this case you no longer have connectivity to Area 4 and Area 44 from the rest of the OSPF domain.

    Try pinging Area 4 and 44 from R5 without a virtual-link with S0/0 down. Then look at R5's routing table once the R5-R4's OSPF adjacency over the Frame-relay is down..

    It's gone!

    % Subnet not in table

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