> On Apr 27, 2016, at 1:00 PM, Sean Conner <s...@conman.org> wrote: > > It was thus said that the Great Mouse once stated: >> >> And I spend over $80/month for DSL to a provider that gives me a /29 >> and a /60 from globally routed space. (That everything is now CIDR >> blocks is another loss; I am not fond of the desupporting of >> noncontiguous subnet masks, even though I can understand it - I'm the >> only person I've ever heard of running that way other than for >> testing.) > > One benefit of contiguous subnet masks is that it makes routing faster. > It's still a linear search,
Not necessarily. You can do a lot better than linear search for route lookup. That can be done with non-contiguous subnet masks too (I remember reading a paper from 30ish years ago on that), but it takes less space -- fewer lookup table entries -- if the subnet masks are contiguous because then each subnet is only one numeric range rather than several. I think the main argument against non-contiguous masks is that it's a feature without a purpose, and a popular source of bugs. paul