User guide

IP Addresses
User Guide 5
IP Addresses
To send mail to a person, you must first know the person’s street
address. When a computer connects to the Internet to send data to
a different computer, it must first know the address of that com-
puter. A computer address is known as an
IP address .
Each computer on the Internet has a unique IP address. An IP
address has four sets of numbers which are divided by decimal
points. Examples of IP addresses are:
• 192.168.0.11
• 10.1.20.18
• 208.15.15.15
A firewall device such as the Firebox® X Edge is also a computer and
thus has an IP address.
Network addressing
Your ISP assigns IP addresses, which are a requirement to connect to
the Internet. IP addresses can be dynamic or static.
Static IP addresses occur when an ISP permanently assigns one or
more IP addresses for a user. This addresses does not change with
time. Because ISPs have a limited number of addresses allocated to
them, they must make efficient use of their addresses.
Dynamic IP addresses allow the ISP to use their address space more
efficiently. Using dynamic IP addresses, the IP addresses of individ-
ual user computers can change with time. If a dynamic address is
not in use (the user is not connected to the network), it can be
automatically assigned to a different computer.
Your ISP can tell you how their system assigns IP addresses.
About DHCP
Many ISPs assign dynamic IP addresses through (Dynamic Host Con-
figuration Protocol (DHCP). When a computer connects to the net-
work, a DHCP server at the ISP assigns that computer an IP address.
It is not necessary to assign IP addresses manually when you use
DHCP.