On 9 October 2014 05:40, Mark Andrews <ma...@isc.org> wrote: > > In message < > 482678376.131852.1412829159356.javamail.zim...@snappytelecom.net>, > Faisal Imtiaz writes: > > >Only short sighted ISP's hand out /56's to residential customers. > > > > I am curious as to why you say it is short sighted? what is the > technical or > > otherwise any other reasoning for such statement ? > > 256 is *not* a big number of subnets. By restricting the number > of subnets residences get you restrict what developers will design > for. Subnets don't need to be scares resource. ISP's that default to > /56 are making them a scares resource.
My moment of clarity came when I got a /56 routed to my house and started using it. I started off thinking that 256 was a huge number of subnets, more than I could ever need. What I realised was that (sticking to best practices) a /56 only allows you one further level of delegation, and I found that to be more of a barrier than the number of subnets. In the same way that you stop thinking "/64 is a lot of addresses" and start thinking "/64 is a network" I find it helps to stop thinking "/48 is 65536 subnets" and start thinking "/48 allows you up to 4 levels of delegation." Dan
