(Internet Protocol address) The address of a device attached to an IP network (TCP/IP network). Every client, server and network device must have a unique IP address for each network connection (network interface). Every IP packet contains a source IP address and a destination IP address.
Static and Dynamic IP
An IP network is somewhat similar to the telephone network in that you have to have the phone number to reach a destination. The big difference is that IP addresses are often temporary.
Each device in an IP network is either assigned a permanent address (static IP) by the network administrator or is assigned a temporary address (dynamic IP) via DHCP software. Routers, firewalls and proxy servers use static addresses as do most servers and printers that serve multiple users. Client machines may use static or dynamic IP addresses. The IP address assigned to your service by your cable or DSL Internet provider is typically dynamic IP. In routers and operating systems, the default configuration for clients is dynamic IP (see DHCP).
Dotted Decimals
IP addresses are written in "dotted decimal" notation, which is four sets of numbers separated by periods; for example, 204.171.64.2. If you knew the IP address of a Web site, you could enter the dotted decimal number into your browser instead of the domain name (which is why we have DNS!).
Although the next version of the IP protocol offers a virtually unlimited number of unique addresses (see IPv6), the traditional IP address (IPv4) uses a 32-bit number that defines both the network and the host computer. The network class determines how many of the 32 bits are used for the network address, leaving the remaining bits for use as the host number (note the numbers of networks and hosts in the table below). The host number can be further divided between subnetworks and hosts (see subnet mask).
Class A, B and C
Although the computer identifies the class by the first three bits of the address (A=0; B=10; C=110), people identify the class by the first number in the address (see range below). This class-based system has also been greatly expanded, eliminating the huge disparity in the number of hosts that each class can accommodate (see CIDR).
Networks, Subnets and Hosts
An IP address is first divided between networks and hosts. The host bits are further divided between subnets and hosts. See subnet mask.
IP - Logical or Physical?
An IP address is somewhat of a hybrid, which can be thought of as either logical or physical, depending on how you view it. It is a unique number assigned to a node, which makes it seem physical, especially because there is so much name-to-IP address resolution going on in the network.
There is also the Ethernet address, which is built into the network adapter. That is indeed physical, and it does not change, which is very typical of physical device names. However, since IP addresses can be dynamically assigned, causing the same client workstation to have a different IP address every day, the IP address seems more like a logical address. Regardless of what it is, it would make a great debate in a computer science class. See logical vs. physical, IPv6, private IP address, TCP/IP abc's and IP on Everything.
Static and Dynamic IP
An IP network is somewhat similar to the telephone network in that you have to have the phone number to reach a destination. The big difference is that IP addresses are often temporary.
Each device in an IP network is either assigned a permanent address (static IP) by the network administrator or is assigned a temporary address (dynamic IP) via DHCP software. Routers, firewalls and proxy servers use static addresses as do most servers and printers that serve multiple users. Client machines may use static or dynamic IP addresses. The IP address assigned to your service by your cable or DSL Internet provider is typically dynamic IP. In routers and operating systems, the default configuration for clients is dynamic IP (see DHCP).
Dotted Decimals
IP addresses are written in "dotted decimal" notation, which is four sets of numbers separated by periods; for example, 204.171.64.2. If you knew the IP address of a Web site, you could enter the dotted decimal number into your browser instead of the domain name (which is why we have DNS!).
Although the next version of the IP protocol offers a virtually unlimited number of unique addresses (see IPv6), the traditional IP address (IPv4) uses a 32-bit number that defines both the network and the host computer. The network class determines how many of the 32 bits are used for the network address, leaving the remaining bits for use as the host number (note the numbers of networks and hosts in the table below). The host number can be further divided between subnetworks and hosts (see subnet mask).
Class A, B and C
Although the computer identifies the class by the first three bits of the address (A=0; B=10; C=110), people identify the class by the first number in the address (see range below). This class-based system has also been greatly expanded, eliminating the huge disparity in the number of hosts that each class can accommodate (see CIDR).
Maximum Maximum Number of
Class Number Hosts Bits used in
Number of per Network/Host
Class Range Networks Network ID ID
A 1-126 127 16,777,214 7/24
B 128-191 16,383 65,534 14/16
C 192-223 2,097,151 254 21/8
127 reserved for loopback test
Networks, Subnets and Hosts
An IP address is first divided between networks and hosts. The host bits are further divided between subnets and hosts. See subnet mask.
IP - Logical or Physical?
An IP address is somewhat of a hybrid, which can be thought of as either logical or physical, depending on how you view it. It is a unique number assigned to a node, which makes it seem physical, especially because there is so much name-to-IP address resolution going on in the network.
There is also the Ethernet address, which is built into the network adapter. That is indeed physical, and it does not change, which is very typical of physical device names. However, since IP addresses can be dynamically assigned, causing the same client workstation to have a different IP address every day, the IP address seems more like a logical address. Regardless of what it is, it would make a great debate in a computer science class. See logical vs. physical, IPv6, private IP address, TCP/IP abc's and IP on Everything.
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2008 The Computer Language Company Inc. All rights reserved. |
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