perl and network addresses

[Jason Stephenson]

Paul Lussier wrote:

> Yes, more or less.  Between you and Jason I've been able to come up
> with exactly what I need.  Thanks a lot for all your help.  Why I
> couldn't see this for myself is beyond me.  Of course, this week has
> been full of me "missing the details" to the point where I somehow
> managed to mail my taxes to myself from work the other day rather than
> to my accountant :) So, just in case you wondered, the USPS system is
> working at peak efficiency !

You're very welcome to the help, and we all have those weeks. It took me 
a while to realize what your real question was.

Once I figured out your question, it was actually rather  interesting: 
adding network addresses to interpolate between different networks. 
Trying to answer it allowed me to discover some facts about IPv4 
addresses and masks, so I got to learn something, too.

The thing that I found most interesting is if you use the one or two 
digit kind of "mask," i.e. /19, you can determine how many addresses are 
on the network via the following C code: addresses = 1 << (32 - n). 
Where n is the part of the mask after the /.

I wish I could find a faster way to blit the bits to make the "real" 
mask from the /N style than using a for loop. Only alternative I can 
think of is to use a switch on the 33 possibilities (0-32).--Of course, 
anything < /8 and > /30 doesn't make a "real" network.

Can anyone think of a better way to blit an arbitrary number of bits 
from 0 to 1?

Now, I'm working on a network calculator application that will support 
IPv6 as well. I should probably do it in JavaScript, uh, sorry, AJAX, so 
that the "Web 2.0" people will notice. ;)

Cheers,
Jason