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This chapter explains more about IP addresses and how
automatic IP configuration works on the Switch.
For details on how to view and amend your Switch’s IP settings,
refer to “IP Settings” on page 23.
How Your Switch Obtains IP Information
Your Switch can obtain IP information using one of the following
methods:
■ Automatic IP Configuration (default) — the Switch will
configure itself with its default IP address
169.254.x.y,where x and y are the last two bytes of the
Switch’s MAC address.
Refer to “Automatic Process” on page 19 for details on how
the Switch automatically obtains IP address information.
■ Static IP Configuration — you can manually input the IP
information (IP address, subnet mask, and default gateway).
Refer to “IP Settings” on page 23. If your computers are
configured with static addresses and you do not wish to
change this, then you should use the Discovery program on
the Switch CD-ROM to detect and configure your Switch.
For details on how to use Discovery to detect the Switch on the
network, refer to “Using Discovery” on page 39.
■ DHCP Addressing — DHCP addressing is a dynamic
mechanism which the Switch uses to obtain an IP address
lease from the DHCP server which is located on your network.
If you select DHCP addressing, you will only be able to find
out the IP address of the Switch by cross referencing the
Switch’s MAC address in the DHCP server’s lease list. Refer to
“IP Settings” on page 23.
3Com recommends that you do not use DHCP Addressing, unless
you have experience of configuring and managing a DHCP server.
How Automatic IP Configuration Works
When your Switch is powered up for the first time the IP
configuration setting is set to
automatic — this is the default
setting.
If your Switch has been powered up before, whichever of the
three options for IP configuration (automatic, static
or DHCP)
was last configured is activated when the Switch powers up
again.
Automatic Process
To detect its IP information using the automatic configuration
process, the Switch goes through the following sequence of
steps:
1 The Switch tries to configure itself with the default IP address
169.254.x.y,where x and y are converted from the last two
bytes of the Switch’s MAC address.
For example, if the MAC address is 08004E000102, the IP
address would be 169.254.1.2. This address is used if the
Switch is operating in a standalone mode, or no other Switches
on the network have this IP address.
2 If this default IP address is already in use on the network then
the Switch detects this, and increments the last byte of the MAC
address by one to generate its IP address. The IP address would
therefore become 169.254.1.3.
AUTOMATIC IP CONFIGURATION