[c-nsp] Access-list Question

[Jeff Kell]

Brian McMahon wrote:

> Cool example -- but it still doesn't answer the fundamental question:  
> Why couldn't the same thing have been expressed as "deny ip any  
> 195.30.0.255 255.255.0.255", like you'd do with a noncontiguous netmask?

I suspect to maintain the distinction between access list entities (which allow noncontiguous bits) and routes (which do not allow noncontiguous bits).  The route/subnet "mask" must be contiguous left-to-right ones followed by contiguous zeroes and can just as easily be done with CIDR notation, while the ACL wildcard is a true bitmask indicating which bits we "don't care" about when comparing addresses.

Jeff (who would have liked discontiguous subnet masks in routes recently)