[quagga-dev 10837] Re: non-sequential netmasks support for RIPv2

Arjun Prasad arjunprasadmca at gmail.com
Thu Oct 24 13:05:06 BST 2013


@James Carlson

>A non-contiguous netmask is one where the 1-bits are not packed in the
>uppermost bits of the mask.  For example, 255.255.1.0 would be a
>non-contiguous netmask, because the uppermost 16 bits are set, but then
>there's a gap of seven 0 bits before the next 1-bit in the mask
Then what is the need for having this non-contiguous netmask concept.
Why this term came? As per doc this term is there in ripV2 rfc (rhough i
didn't find).


On Thu, Oct 24, 2013 at 5:16 PM, James Carlson <carlsonj at workingcode.com>wrote:

> On 10/24/13 01:59, Arjun Prasad wrote:
> > Hi Team,
> > While going through a Quagga document, i came across following line.
> > "Quagga ripd does not support the non-sequential netmasks that are
> > included in RIP Version 2. "
> > What do we mean by " non-sequential netmasks" can anybody explain me
> > with example or send a link where i can find some detail.
>
> By "non-sequential," I believe the documentation actually means
> "non-contiguous."  That text dates back to Zebra.
>
> A non-contiguous netmask is one where the 1-bits are not packed in the
> uppermost bits of the mask.  For example, 255.255.1.0 would be a
> non-contiguous netmask, because the uppermost 16 bits are set, but then
> there's a gap of seven 0 bits before the next 1-bit in the mask.  By
> contrast, 255.255.128.0 would be a normal, contiguous netmask, also
> known as "/17" in CIDR notation.
>
> Among other things, a non-contiguous netmask is not representable using
> CIDR notation.  Perhaps most importantly, it's completely unnecessary as
> the size of a subnetwork is defined by the total number of zeros in the
> netmask, not their positioning, so allowing non-contiguous
> representations doesn't really help anyone.
>
> > I am willing to add this feature in Quagga's RIP.
>
> Please don't add non-contiguous netmask support.  It's foolish.
>
> --
> James Carlson         42.703N 71.076W         <carlsonj at workingcode.com>
>
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