3Com 4200G Getting Started Manual page 61

The switch's IP address was entered correctly in your network
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management application (such as 3Com Network Director).
The following is a brief overview of IP addressing, and how to obtain a
registered IP address.
IP Addressing
To be managed correctly, each device on your network (for example a
switch or a hub) must have a unique IP address. IP addresses have the
format n.n.n.n where n is a decimal number between 0 and 255. An
example IP address is 192.168.100.8. The IP address is split into two
parts:
The first part ('192.168.100' in the example) identifies the network on
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which the device resides
The second part ('.8' in the example) identifies the device within the
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network
The natural subnet mask for this example is 255.255.255.0.
If your network is connected to the external IP network, that is, you
access the Internet, you must apply for a registered IP address.
How do you obtain a registered IP Address?
The IP registration system ensures that every IP address used is unique; if
you do not have a registered IP address, you may be using an identical
address to someone else and your network will not operate correctly.
InterNIC Registration Services is the organization responsible for
supplying registered IP addresses. The following contact information is
correct at time of publication:
World Wide Web site: http://www.internic.net
If your IP network is internal to your organization only, that is, you do not
access the Internet, you may use any arbitrary IP address as long as it is
not being used by another device on your network. 3Com suggests that
you use addresses in the range 192.168.0.0 to 192.168.255.255 with a
subnet mask of 255.255.255.0.
These suggested IP addresses are part of a group of IP addresses that
have been set aside specially for use 'in house' only.
Solving Communication Problems 61