What Is an IP Address?
FRITZ!Box Fon WLAN 7170 – 8 Network Settings
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Public IP Address
A public IP address is an IP address valid in the Internet. Ev-
ery computer or router participating in the Internet must
have a uniquely assigned public IP address. This address is
usually negotiated dynamically with the Internet Service Pro-
vider when a connection to the Internet is dialed. The Inter-
net Service Provider assigns the negotiated IP address to the
computer or router for the duration of an Internet session.
Private IP Address
Private IP addresses are used for computers and other net-
work devices within local IP networks.
Since many local IP networks are not connected to the Inter-
net except via single computers or routers (gateway), certain
address ranges are excluded from the publicly available IP
addresses so that they are available for assignment in local
IP networks. An IP address may only be assigned once within
the local network. A private IP address may exist in any num-
ber of other local networks.
Fixed IP Address
Fixed IP addresses are IP addresses which are permanently
assigned to a computer or another device like a network
printer.
Assigning fixed IP addresses makes sense in cases where a
local network has a sufficiently large pool of IP addresses
available, or when a computer is always supposed to be ac-
cessible at a certain address (such as a web server or an e-
mail server).
Dynamic IP Address
A dynamic IP address is an IP address valid only for the dura-
tion of one Internet or network session.
Every computer participating in the Internet must have a
uniquely assigned public IP address. Since only a limited
number of such IP addresses is available, they must be used
sparingly. That is why most of the Internet participants who
dial in to the Internet receive a dynamic IP address. They are
