It did not say you had to summarize into one route. Answer C means you
would need two routes, but it is better than advertising networks which do
not originate from your domain...
----- Original Message -----
From: Priscilla Oppenheimer <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, February 04, 2001 3:26 PM
Subject: Re: Subnet questions
>
> >
> > > Ok, I looked into the resources that you've referred to, and put a
little
> > > more thought into this question.
>
> Make sure the resources cover supernetting and not just subnetting. The
> goal of supernetting is to group routes together so that a router reduces
> the number of routes it tells other routers about. That's very different
> from subnetting where the goal is to subdivide the network number assigned
> to you by your ISP or ARIN.
>
>
> > > So, we're given the networks,
> > >
> > > 192.168.9.0 (192.168.0000 1001.0000 0000)
> > > 192.168.10.0 (192.168.0000 1010.0000 0000)
> > > 192.168.11.0 (192.168.0000 1011.0000 0000) and
> > > 192.168.12.0 (192.168.0000 1100.0000 0000).
>
> The question was, "When using classless supernetting, which route best
> summarizes the following networks?"
>
> So we're looking for one route that will let us tell other routers about
> our four networks. The possible answers were:
>
> A) 192.168.0.9 / 20 obviously wrong because of the .9 at the end
>
> B) 192.168.0.0 / 16 this could work, but it's less specific than answer
D
>
> C) 192.168.9.0 / 22 this doesn't work because it leaves out
> 192.168.12.0, plus it would be stupid to use .9 when the one bit isn't
even
> referred to with a /22. The one bit is in the node ID (suffix) part of the
> addresses.
>
> D) 192.168.8.0 / 21 this works
>
>
> > >
> > > Keeping in mind that the question asks for the "best" summarization...
> >since
> > > 192.168.8.0/21 would include additional networks not mentioned in the
> > > problem (i.e. 192.168.13.0, 192.168.14.0, etc.), I can see how this
might
> > > not be the best answer.
>
> With a /21, the one bit and two bit don't matter so 13 and 14 don't
matter.
> Those bits are in the node part when we use /21.
>
> > >
> > > 192.168.9.0/22, on the other hand, is the "best" summarization for the
> >first
> > > three networks. The last network has no other networks to be
summarized
> > > with, therefore can be left out of the summarization.
>
> The goal is to group all four networks. Leaving out one would cause you
not
> to meet that goal. I think D is the right answer.
>
> Priscilla
>
> > >
> > > Is this the right reasoning for the correct answer being C?
> > >
> > >
> > >
> > > Regards,
> > >
> > > Han-Song Kim
> > > Network Engineer, CCNP/ MCSE/ MCDBA
> > > Planetary Networks
> > > (W)408.745.3065 (C)408.910.7907
> > > [EMAIL PROTECTED]
>
>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
>
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