Hi sina...
what you told about Bit B of the ABR(R3) in this
reply....
When an ABR is connected to 2 or more areas according
to RFC2328 Bit B should be set...(page127.).
can you explain what you mean in your answer..
Alex

--- Sina Mirtorabi <sinaCISCO.COM> wrote:
> Dhaval,
>
> Dhaval Shah wrote:
>
> > Hi,
> > I have a question about Alternate ABR
> behavior for which I could not
> > find the answer from the working group archive.
> >
> > Backbone
> > R1----------------R2
> > |
> > |
> > | area 1
> > |
> > R3----------------R4
> > area 2
> >
> > R3 is the modified ABR (according to the
> alt-abr-draft), who doesnt have a
> > backbone connection. It does include summary LSAs
> from both areas 1 and 2 into
> > its SPF calculation and will thus forward traffic
> destined to backbone and
> > other areas.
>
> correct, since R3 won't bit the B bit set ( it
> doesn't consider itself as ABR ) it can
> consider summary from a non-backbone area
>
> >
> > However, R1 has an active backbone
> connection and hence it will only include
> > summary LSAs from backbone into its SPF
> calculation, thus not including
> > summary LSAs generated by R3 (for area 2).
>
> it's true that R1 doesn't consider the summary from
> non-backbone area but actually R3
> does not generate any summary. remember R3 is not
> considering itself as ABR
>
>
> > Hence it will not know how to reach
> > area 2 and R4.
> > Is this true? Is there a way around this
> problem other then configuring a
> > virtual link between R3 and backbone? It seems
> like the alternate ABR
> > modification wont solve this problem.
> >
>
> your above scenario would need a virtual link, the
> alternate ABR is not solving this
> problem however refer to the draft as you have 2
> example where this is useful to have
> alternate ABR behavior
>
>
> Sina
>
>
>
> >
> > thanks
> > Dhaval.
> >
> > ------- End of Forwarded Message

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