subnets

[carl_townshend]

as a quick guide, what is the rule of thumb for subnetting, say for lots of small networks subnet a class c etc, and for lots of hosts and networks subent a class a ? is this right ?

[Joseph W. Doherty]

If you're working with classful addressing, more or less yes. (Also don't forget class B.)

If you're working with classless, you only really need to consider what the total address block permits since you can subdivide it as you desire.