Alex,
        Actually you do keep multiple routes to a router destination.
        For instance, if an ASBR is reachable in multiple area's via different
paths, you must store a routing table entry for each path regardless of cost.
        It is only in the case of IP routes that you store only the "best
route/routes" to a destination.
Nikhil

"Xie, Feng" wrote:

> Hi, Alex:
>
> Usually, we only keep the best route to a destination. As you said, at
> any time, there may be only one entry for an ASBR with multiple next hops
> due to equal-cost multipath. My understanding is that what described in the
> RFC is a process to build the best route to an ASBR when you have choice
> among multiple routes. It does not mean that an implementation has to keep
> all possible routes to an ASBR.
>
> Feng Xie
>
> -----Original Message-----
> From: alex lerin [mailto:alexlerinYAHOO.COM]
> Sent: Thursday, August 23, 2001 5:43 AM
> To: OSPFDISCUSS.MICROSOFT.COM
> Subject: About ASExternal calculation
>
> Hi..
> I have a doubt in ASExternal Calculation...
>
> In ASExternal calculations of RFC2328, Section
> 16.4,3rd point 3rd paragraph,it says that if the
> forwarding address is zero,th packet should be sent to
> the ASBR itself.Also it says that we have to prune for
> multiple entries.
> My doubt is that how can we prune when there is
> always only one entry for the ASBR in the routing
> table.Because whenever we get a destination ,we check
> for its entry in the routing table and compare the
> path type etc.,and if thay are equal cost we only add
> the next hop entry to the route and not a different
> entry.So there is no possibility for multiple entries
> for the same ASBR in the routing table.
> If I am wrong tell me when can there be more than
> one entries for the same ASBR in the routing table?
>
> Thanks in advance
> Alex
>
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Nikhil Sama                     E-Mail: Nikhil.Samanexsi.com
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