Fw: Re: Network Address/Netmask Notation

[Keith Morse]

On Sun, 23 Mar 2003, David A. Bandel wrote:

> With non-VLSM CIDR, we can't use /#.  We will also get very large
> headaches trying to calculate which IPs are found on a network with
> absurd netmasks like 255.255.255.123.  If you don't think this is valid,
> you can try it on your network and see that it works just fine with the
> following values:
> network: 192.168.0.1
> netmask: 255.255.255.123
> broadcast: 192.168.0.133
> hosts:  192.168.0.5, 192.168.0.129
> yes, for this particular netmask, there are only 2 hosts, other non-VLSM
> netmasks give varying numbers of hosts in different patterns scattered
> about between the network and broadcast numbers.


Wild, I've never seen non-contigous netmasks before.  Is this legal per 
the ip specifiation, or just the result of the xor/nor (sorry don't 
remember the boolean operation involved between ip and netmask) operation?






> Note:  since I'm not a masochist and don't like headaches (or anding
> binary netmasks w/ addresses), I use a program to calculate the above
> just as the kernel does.
> 
> Ciao,
> 
> David A. Bandel
>