>
> > 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
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
