[quagga-dev 10836] Re: non-sequential netmasks support for RIPv2

James Carlson carlsonj at workingcode.com
Thu Oct 24 12:46:07 BST 2013


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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