You received a correct response to the main part of your problem, so I won't 
address it, although I don't know why you ought to notify your ISP that your 
IP pool doesn't meet your needs. I'm quite partial myself to running a 
private IP network in almost all instances, using NAT on the router to expose 
a single IP address, since it's a big security problem to expose your network 
to the Internet without a firewall.
 AY> (ii) configure DHCP so that each of the roughly 30 PCs on each segments
 AY> receives an ip address?
Load inetcfg first, to migrate your networking commands into the higher level
configuration utility. Then, load dhcpcfg. This utility is nearly 
self-explanatory.
Jeff
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