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What is a subnet? A subnet is a portion of
a larger network address. A subnet address and a subnet mask define subnets. These
allow the administrator to physically separate related machines and differentiate
between local and remote IP traffic. Hosts on subnets are able to communicate
across a routed network, which is ideal for separating workgroups within a company
or smaller companies when attached to one ISP.
 Can
I run subnets across multiple sites? Yes. It is a practical and reasonable
way of utilising your IP allocation, particularly where there are few clients
at each site.
Can
I reserve IP allocations for future use? No. IPs are allocated as and
when they are needed.
What
is 'private' address space? Private address space is an IP range that
has been set aside for internal Networks. It can be used behind firewalls and
on Networks not connected to the Internet.
Does
it matter which IPs I use behind my firewall? Yes. If you arbitrarily choose
IPs to use behind a firewall and the IPs you choose are in use by another organisation,
you will be unable to contact them.
When
can I use private address space? Whenever there is no routed connection
between your network and the Internet, you can use private address space.
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