Hi Ilan,
   Thanx again.
    Another doubt I have is abt the RFC1583 comp.If this is disabled we
have to prune for ASBR entries in the routing table.
    What I understand is pruning means making it to one entry with least
cost(Largest Areaid).
    Is it right?
Thanx in advance
Umesh

-----Original Message-----
From: Ilankumaran N [mailto:nilankuascend.com]
Sent: Friday, July 20, 2001 3:53 PM
To: Umesh_MS
Subject: RE: [OSPF] FW: Re: Doubt aboutType 5 route calculation

Yes.. depending on the type of the external route. Look at the external
type-1 and type-2 definitions in the RFC2328. In any case you will have
to
do the cost comparison.

yes, there is a concept of third-party gateway. i.e, when you, the
actual
gateway and to whom you advertise share a common ip-subnet, you can set
the
next_hop as the actual gateway while advertising a route to your
neighbor
instead of the conventional next-hop-self concept.

Thanks
Ilan

> -----Original Message-----
> From: Mailing List [mailto:OSPFDISCUSS.MICROSOFT.COM]On Behalf Of
> Umesh_MS
> Sent: Friday, July 20, 2001 3:32 PM
> To: OSPFDISCUSS.MICROSOFT.COM
> Subject: [OSPF] FW: Re: Doubt aboutType 5 route calculation
>
>
> Hi Ilan,
> Thanks for your reply..
> I got ur point that u have mentioned .I still have a doubt in that
> section.
> When forwarding address is zero, should we also go for cost
> calculation,looking up the rt entry for destination as in 4th,5th,6th
> point etc in section 16.4 of rfc2328 .If yes then is it only the next
> hop concept changes here.
> Please explain me about this.
> Thanx in advance
> Umesh
>
> -----Original Message-----
> From: ilankumaran
> Sent: Friday, July 20, 2001 3:03 PM
> To: OSPFDISCUSS.MICROSOFT.COM
> Subject: Re: Doubt aboutType 5 route calculation
>
>
> When the forwarding address is set to 0.0.0.0, then the exit point for
> this
> destination is the ASBR which originated the LSA. Then look up the RT,
> for
> an entry to reach the ASBR. If the forwarding address is non-zero,
then
> the
> exit point for this destination is different from the one that
> originated
> the LSA. In this case you need to look up your RT for an entry to
reach
> the
> forwarding address.
>
> consider,
>
> asbr----|
> | |------fwd
> |
> |
> DUT
>
> when asbr imports an external route into your AS, it can set the
> next_hop
> (forwarding address) to either itself or a third party gateway (a
> forwarder). So depending upon what forwarder address being set in the
> LSA
> and the type of the external LSA, DUT can calculate the cost to reach
> external network and select the least one.
>
> Thanks
> Ilan
>
> > -----Original Message-----
> > From: Mailing List [mailto:OSPFDISCUSS.MICROSOFT.COM]On Behalf Of
> > Umesh_MS
> > Sent: Friday, July 20, 2001 2:15 PM
> > To: OSPFDISCUSS.MICROSOFT.COM
> > Subject: [OSPF] Doubt aboutType 5 route calculation
> >
> >
> >
> >
> >
> > Hi,
> > In section 16.4 of ASExternal route calculation in RFC 2328,I am
not
> > very clear with what to be done when forwarding address is zero and
> when
> > it is non-zero.
> > Should we only compare routes when the forwarding address is non
zero
> or
> > must be done for even when the forwarding address is zero.
> > Point 3 and 4 are they related with forwarding address in this
> section.
> >
> > Thanx in advance
> > Umesh
> >
>

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