Re: Stupid Question maybe?

[Adam Atkinson <ghira () mistral co uk>]

On 19/12/2018 16:24, Naslund, Steve wrote:

> It has ALWAYS been the only correct way to configure equipment and is
> a requirement under CIDR.  Here were your commonly used netmasks
> before CIDR/VLSM :
>
> 255.0.0.0 255.255.0.0 255.255.255.0
>
> Which one is not contiguous?

There is an example in RFC950 on page 15.

   3.  A Class C Network Case (illustrating non-contiguous subnet bits)

      For this case, assume that the requesting host is on class C
      network 192.1.127.0, has address 192.1.127.19, that there is a
      gateway at 192.1.127.50, and that on network an 3-bit subnet field
      is in use (01011000), that is, the address mask is 255.255.255.88.

Admittedly, page 6 contains:

      Since the bits that identify the subnet are specified by a
      bitmask, they need not be adjacent in the address.  However, we
      recommend that the subnet bits be contiguous and located as the
      most significant bits of the local address.

I have never seen noncontiguous network masks used in real life, but I 
may not be old enough.

--
Adam Atkinson