Re: CIDR and VLSM

VLSM means taking a classful address and breaking it up along non-classful
boundaries - take a class C address and break it up into 2 /25s, 4 /26s, 16
/28s, or any combination thereof (as long as the subnet combination runs
along bit boundaries).

CIDR notation allows you to refer to the number of bits in a netmask rather
than the netmask itself - instead of 10.1.1.16 netmask 255.255.255.240, you
can just write it 10.1.1.16/28 - meaning there are 28 bits in the mask used
to subnet this address.

With CIDR, you can take multiple classless subnets (see VLSM) and aggregate
them together or 'supernet' them - for instance you can take two contiguous
/24 addresses and write it as a /23 - allows for smaller routing tables at
your edge or boundary routers.

Hope this helps
Michael

On Thu, May 14, 2009 at 6:59 PM, Khurram Noor <
engr.khurramnoor_at_googlemail.com> wrote:

> Hello everyone,
>
> What is the real difference between the two terms CIDR and VLSM? Its
> confusing sometimes.
>
> --
> Khurram Noor
> Internetwork Professional
>
>
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Received on Thu May 14 2009 - 19:26:56 ART