Subrat

actually there is a virtual link between R10 and R11 in order to link the area 3
to the backbone
if the link between R6-R10 goes down R10 won't be ABR any more and area 3 will
be disconnected from the backbone
here is another example

                       R2
                    / \
            / \
    / \
R1--------------------------R3
| |
| |
| |
R5 R4

R1-R5 is in area 1
R1-R3 area 0
R3-R4 area 2
R1,R2,R3 area 3

if the backbone link between R1-R3 is broken you need a virtual link through R2
in order to maintain the connectivity
virtual link could also be used in order to have control over the traffic as
intra area path are always preferred over Inter area path by playing with
virtual link you could make the traffic go through the desired path

Sina

Subrat Mohanty wrote:

> I have a basic doubt in Virtual Link. I am still not clear about the use or
> benifit of the VLink.
>
> Pl. Check RFC-2328 Fig-6. Sec-3.4. See the last line which states
>
> "Note that a failure of the line between Routers RT6 and RT10 will cause the
> backbone to become disconnected. Configuring a virtual link between Routers
> RT7 and RT10 will give the backbone more connectivity and more resistance to
> such failures. "
>
> Anyway RT7 and RT10 are connected thru network-6 and all the routers are
> having this info so that when the link fails between RT6-RT10 fails they can
> still do the routing. What is the benifit of the Vlink?
>
> Can u pl. give me a scenario where I will have an advantage of a VLink?
>
> Regards Subrat

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