[Gllug] DHCP & DNS

[Ian Northeast]

Leigh Mason wrote:
> 
> hold on, i thought it was one of the  rfcs that stated, when using class A
> addresses the first bit must always be off, class b must always start
> 10xxxxxx and class c is 110xxxxx. any address that starts from 192 - 223 is
> a class c.
> and i think the rfcs also state default subnet masks to be used for each
> address, therefor 192.168.0.0/16 is not a default subnet, you have borrowed
> hosts bits to create a new subnet - why bother?

There is an RFC which states this but it is out of date. There is no
such thing as a network class any more and any network number can be
used with any network mask (as long as you stay out of the multicast
etc. ranges). So using 192.168/16 or 10.x.x/24 are both perfectly valid.

Many OSs (and indeed routers - Ciscos can be guilty of this) still
default to classful routing but it can always be disabled.

Regards, Ian

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