[Gllug] DHCP & DNS

[David Damerell]

On Friday, 7 Dec 2001, Leigh Mason wrote:
>From: David Damerell <damerell at chiark.greenend.org.uk>
>>On Thursday, 6 Dec 2001, Leigh Mason wrote:
>>>why not use a 192.168.0.0/24. (192.168.0.1 - 254) This is a class C address
>>>reserved for private networks and is much easier to keep track of host
>>>addresses. (254) possible hosts.
>>No! Not 192.168.0.0/24! Pick a _random_ subnet of 192.168.0.0/16 or
>>the reserved class Bs specified in RFC 1918. Does no-one actually read
>>any standards anymore?
>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. 

Eh. You know that, in the CIDR world, classes are somewhat dead,
existing only as a convenient piece of terminology? For instance, some
of the old class As are now divided up between many cable modem and
xDSL providers.

>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?

This is rather incoherent to reply to, but 192.168.0.0/16 is the range
in which you will find the set of 254 reserved class C (/24)
subnets. You'll notice that I do not suggest using all of it, but a
random (implied class C) subnet of it.

-- 
David Damerell <damerell at chiark.greenend.org.uk> flcl?

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