Re: HELP : How to group IP addresses by refering to them as a single name ?

["Darrell A. Escola" <darrell-iptables@descola.net>]

On Fri, Sep 20, 2002 at 02:11:29PM +0100, Antony Stone wrote:
>
> On Friday 20 September 2002 1:43 pm, Alok Shukla wrote:
> 
> > HI,
> >
> > THANKS A LOT..!
> >
> > I have understood a lot of things. Now just for the
> > sake..tell me if the following are valid
> >
> > iptables -t nat -A POSTROUTING -s 192.168.0.10/27 -d
> > any/0 -J MASQUERADE
> >
> > for allowing all the machines starting from 11 to 41
> 
> Unfortunately not.   You have the right idea, but you can't simply choose the 
> starting address anywhere you like :-(
> 
> The rule is this: the starting address of the block must be a multiple of the 
> size of the block.
> 
> So if you're creating a block of 64 machines with a /26 netmask, the first 
> address of the block must be 0, 64, 128 or 192.
> 
> Similarly, if you want a block of 32 machines with a /27 netmask, the first 
> address of the block must be 0, 32, 64, 96, 128, 160, 192 or 224.
> 
> In yur case you tried to create a block of 32 machines with a starting 
> address of 10, which I'm afraid is not allowed :-)
> 
> 
> Hope this helps,
> 
> Antony.
> 

It might be well to note that the "0" host address is reserved for the
network and not useable as a host/node address - the last address in the
subnet is reserved for broadcast - therefore a /27 subnet allows 30 host
addresses. If more than 30 host addresses are needed, use a /26 subnet,
allowing 62 hosts.

-- 
Darrell A. Escola, CCNA(R)
Cisco(R) Certified Network Associate

This message emanates from my personal domain, and conveys solely my own
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