Hosts (file), what is this?

The hosts file is a computer file used in an operating system to map hostnames to IP addresses. The hosts file is a plain-text file and is conventionally named hosts.

Contents:

• Purpose
• File content
• Location in the file system
• History
• Extended applications
• Security issues
• See also
• References
• External links

Purpose

The hosts file is one of several system facilities to assist in addressing network nodes in a computer network. It is a common part in an operating system's Internet Protocol (IP) implementation, and serves the function of translating human-friendly hostnames into numeric protocol addresses, called IP addresses, that identify and locate a host in an IP network.

In some operating systems, the hosts file content is used preferentially over other methods, such as the Domain Name System (DNS), but many systems implement name service switches (e.g., nsswitch.conf) to provide customization. Unlike the DNS, the hosts file is under the direct control of the local computer's administrator.

File content

The hosts file contains lines of text consisting of an IP address in the first text field followed by one or more hostnames. Each field is separated by white space (blanks or tabulation characters). Comment lines may be included; they are indicated by a hash character (#) in the first position of such lines. Entirely blank lines in the file are ignored. For example, a typical hosts file may contain the following:

# This is an example of the hosts file

127.0.0.1 localhost loopback

::1 localhost

To reset the Hosts file back to the default, follow these steps:

1. Click Start, click Run, type %systemroot% \system32\drivers\etc, and then click OK.
2. Rename the Hosts file to Hosts.old.
3. Create a new default hosts file. To do this, follow these steps:

• Right-click an open space in the %WinDir%\System32\Drivers\Etc folder, point to New, click Text Document, type hosts, and then press Enter.
• Click Yes to confirm that the file name extension will not be .txt.
• Open the new Hosts file in a text editor. For example, open the file in Notepad.
• Copy the following text to the file:

For Windows XP or for Windows Server 2003

# Copyright (c) 1993-1999 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

127.0.0.1 localhost

For Windows Vista or for Windows Server 2008

# Copyright (c) 1993-2006 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

127.0.0.1 localhost
::1 localhost

For Windows 7

# Copyright (c) 1993-2006 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

# localhost name resolution is handle within DNS itself.
# 127.0.0.1 localhost
 # ::1 localhost

     4. Save and then close the file.