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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