A IP address (Internet Protocol address) is a date, which e.g. permits a logical addressing of network services in IP networks like the Internet. Are on a host (e.g. Computers, rout, printer, IP telephone) or several of these network services actively, possesses the equipment at least at one time one IP address, which is clear in its Subnetz. Thus IP addresses make possible to communicate to the services in the network with one another.

Most simply one can compare this IP address with a telephone number. A telephone connection can be selected clearly over a telephone number like a Web server under its clear IP address is attainable e.g.

Bases

In order to develop communication between two technical devices, each of the devices must be able to send to the other equipment data. So that these data arrive with the correct receiving station, the receiving station must become clearly designated (addressed). This happens in IP nets with a IP address.

IP address in IP packets

IP addresses (Internet minutes addresses) are registered in each IP package in the pouring and goal address arrays (to header format see IPv4#Header-Format). Each IP package contains thereby both the address the transmitter and those of the receiver.

Major item: IP package

Structure

IPv4

Thus 4 of Oktetts of 32 bits, (byte) consists the IPv4-Adressen used predominantly since the introduction of the version 4 of the Internet Protocols. Thus 232, thus 4.294.967.296 addresses are representable. In the dotted decimal notation the 4 of Oktetts is written as four decimal numbers from each other separated by points within the range of 0 to (inclusively) 255, example: 130.94.122.195.

Major item: IPv4

IPv6 - new version with larger address area

By the rapidly rising need of IP addresses it is foreseeable that the usable address area of IPv4 will be exhausted sooner or later. Particularly for this reason IPv6 was developed. It uses 128 bits for the storage of addresses, thus is 2128 = 25616 (= 340.282.366.920.938.463.463.374.607.431.768.211.456 = 3.4 1038) addresses representably. This number is sufficient, over for each square meter of the earth's surface at least 665.570.793.348.866.943.898.599 (6.65 1023)

To make available IP addresses. Thus no address area problems should have to be feared when using IPv6 in foreseeable future.

Since the decimal notation would be ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd.ddd unclear and badly manageable, one represents IPv6 addresses in hexadecimals. In order to simplify this representation further, 2 of Oktetts of the address is summarized in each case and represented separately into groups by colon. : : : : : : : (each colon separates two of Oktetts of the address). Example: fe80: 0: 201: 8033: fe3d: 1957: a24a: 52ea

Major item: IPv6

Network part and component

Each IP address is separated by a net mask into a network and a component (host part). The bits (network part), masked by the net mask, are identical with all host of a net. The information, whether equipment lies in the same network (i.e. same network part in the IP address), from a host needed, in order Routing decisions to meet to be able (see the following section).

Example: IP address 130.94.122.195 /27

              Decimally binary computation IP address 130.094.122.195 10000010 01011110 01111010 11000011 IP address net mask 255.255.255.224 11111111 11111111 11111111 11100000 AND net mask network part of 130.094.122.192 10000010 01011110 01111010 11000000 = network portion of IP address 130.094.122.195 10000010 01011110 01111010 11000011 IP address net mask 255.255.255.224 11111111 11111111 11111111 11100000 AND EMERGENCY net mask component 3 00000000 00000000 00000000 00000011 = component 

In the case of a net mask with 27 set bits a network part of 130.94.122.192 results. Remain 5 bits and thus 25=32 addresses for the component. Of it still 1 each addresses are needed for the network and for the Broadcast, so that 30 addresses are available for devices.

Major item: Net mask

Routing

If equipment wants to dispatch a IP package, the network parts of the source IP address and goal IP address are compared. If they agree, the goal host is in the same network and the package is sent directly to the receiver. In case of of Ethernet networks ARP minutes serve the hardware address for finding.

If the network parts do not agree against it, then over a Routingtabelle the IP address of a Routers (NEXT hop) is looked for and the package at these routs sent. This has one or more interfaces over contact to other networks and routet the package with the same procedure - he consulted in addition for his part its own Routingtabelle and sends the package to the next routs if necessary or to the goal. Up to the terminal the package knows many networks and routs to go through. Going through a Routers is called also Hop (jump), the Routingverfahren NEXT Hop Routing.

Routing of a HTTP/TCP connection over three networks

Rout has thereby for each of his interfaces an own IP address and net mask, which belong to the respective network. Each IP package is geroutet individually. The pouring and destination address in the IP header are set by the transmitter and remain unchanged during the entire way.

Major item: Routing

Special IP addresses

The net 127.0.0.0 /8 refers to the local computer (loop-bake ADDRESS). From this network area often the address 127.0.0.1 with the host name local host is accessible. Addresses from this range serve for communication of a Client with a server process on the same computer. By means of ssh local host or ftp 127.0.0.1 the servers (sshd, ftpd) on a local computer can be addressed, approximately for testing/trying out.

The special address 255.255.255.255 can be likewise used apart from the highest device address in the net as Broadcastadresse. Thus dispatching of Broadcasts without knowledge of further network parameters is possible. This is important for minutes such as BOOTP and DHCP.

The address range 224.0.0.0 /4 (addresses 224.0.0.0 to 239.255.255.255) is reserved for multicast addresses. Thus there are three IP address types:

• Unicast - sending to a certain receiver in the Internet (normal addressing)
• Broadcast - sending to all devices in the same network (Subnetz)
• Multicast - Send to some devices in the same network (or devices in the MBONE network)

RFC 3330 gives information over the special IP addresses defined at present.

DNS - Translation of computer names in IP addresses

Over the world-wide available Domain Name System DNS names can be transformed into IP addresses (and vice versa). The name www.denic.de results in for example 81.91.161.19 (conditions: 27. January 2006).

Major item: Domain Name System (DNS)

Articles in category "IP address"

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