The host name (including site name ) is the unique name of a computer on a network. It is mainly in the electronic data exchange ( eg e- mail, Usenet, FTP ) is used to specify the communication partner in a human readable and noticeable format. The implementation of the hostname in a machine-readable address is on the Internet today mainly via the Domain Name System (DNS), historically in the file / etc / hosts. In local networks, the reaction is carried partly by DNS, some still with NIS and other protocols. What names are technically allowed, governs the protocol used in each case for name resolution - on the internet so the Domain Name System.

Host name as the name of a physical system

The host name of a physical system (computers, host) is the name under which the system itself knows and with which the system reports. Visible, that host name, if a computer system sends an email, for example, in the sender of status messages or bounce messages or when a user logs on to a server. The host name can be set on UNIX -like systems with the command hostname and read.

The local part of the hostname of physical systems can be chosen freely. Often it is used to the purpose of the computer ( eg, ns, mail, ftp, serv1, SERV2, SERV3 etc. ) to identify, often he is but also arbitrarily on the basis of figures from literature and film, mythical creatures awarded or gods.

Host name as the name of a network node

In the Domain Name System AAAA resource records and A resource records are entered, assign a name an IP address. This name may, but need not be the host name that the host performs with this IP address. This can allow a host to by different names is achievable.



Hostnames are made, as all domain names of several " labels" that are separated from each other by a dot. Each label must be 1-63 characters long, maximum of the domain name may include a total of 255 characters.

Unlike domain names Hostnames may only consist of the ASCII characters az or AZ ( between upper and lower case letters are not distinguished ), 0-9, and the hyphen -minus - exist. The individual labels can not begin or end with a hyphen. Other special characters as the hyphen ( and the point between the labels ) are not allowed, although they are sometimes used anyway. Underscores are often used on Windows systems, although they are not allowed according to RFC 952. Some systems, such as DomainKeys and the SRV resource record, use the underscore intentionally to ensure that their particular domains are not confused with hostnames. Since only certain systems verify the validity of hostnames that use invalid characters has led, for example, as of the underscore to various problems in systems that are connected to the world.


  • September 20, 1971
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  • October 1985
  • October 1989