Apache IP-based Virtual Host Support
Apache IP-based Virtual Host Support
What is IP-based virtual hosting
IP-based virtual hosting is a method to apply different directives based on the IP address and port a request is received on. Most commonly, this is used to serve different websites on different ports or interfaces.
In many cases, name-based virtual hosts are more convenient, because they allow many virtual hosts to share a single address/port. See Name-based vs. IP-based Virtual Hosts to help you decide.
As the term IP-based indicates, the server must have a different IP address/port combination for each IP-based virtual host. This can be achieved by the machine having several physical network connections, or by use of virtual interfaces which are supported by most modern operating systems (see system documentation for details, these are frequently called "ip aliases", and the "ifconfig" command is most commonly used to set them up), and/or using multiple port numbers.
In the terminology of Apache HTTP Server, using a single IP address but multiple TCP ports, is also IP-based virtual hosting.
How to set up Apache
There are two ways of configuring apache to support multiple hosts. Either by running a separate
httpd daemon for each hostname, or by running a single daemon which supports all the virtual hosts.
Use multiple daemons when:
- There are security partitioning issues, such as company1 does not want anyone at company2 to be able to read their data except via the web. In this case you would need two daemons, each running with different
- You can afford the memory and file descriptor requirements of listening to every IP alias on the machine. It's only possible to
Listento the "wildcard" address, or to specific addresses. So if you have a need to listen to a specific address for whatever reason, then you will need to listen to all specific addresses. (Although one
httpdcould listen to N-1 of the addresses, and another could listen to the remaining address.)
Use a single daemon when:
- Sharing of the httpd configuration between virtual hosts is acceptable.
- The machine services a large number of requests, and so the performance loss in running separate daemons may be significant.
Setting up multiple daemons
Create a separate
httpd installation for each virtual host. For each installation, use the
Listen directive in the configuration file to select which IP address (or virtual host) that daemon services. e.g.
It is recommended that you use an IP address instead of a hostname (see DNS caveats).
Setting up a single daemon with virtual hosts
For this case, a single
httpd will service requests for the main server and all the virtual hosts. The
VirtualHost directive in the configuration file is used to set the values of
CustomLog configuration directives to different values for each virtual host. e.g.
<VirtualHost 172.20.30.40:80> ServerAdmin [email protected] DocumentRoot "/www/vhosts/www1" ServerName www1.example.com ErrorLog "/www/logs/www1/error_log" CustomLog "/www/logs/www1/access_log" combined </VirtualHost> <VirtualHost 172.20.30.50:80> ServerAdmin [email protected] DocumentRoot "/www/vhosts/www2" ServerName www2.example.org ErrorLog "/www/logs/www2/error_log" CustomLog "/www/logs/www2/access_log" combined </VirtualHost>
It is recommended that you use an IP address instead of a hostname in the directive (see DNS caveats).
Specific IP addresses or ports have precedence over their wildcard equivalents, and any virtual host that matches has precedence over the servers base configuration.
Almost any configuration directive can be put in the VirtualHost directive, with the exception of directives that control process creation and a few other directives. To find out if a directive can be used in the VirtualHost directive, check the Context using the directive index.
SuexecUserGroup may be used inside a VirtualHost directive if the suEXEC wrapper is used.
SECURITY: When specifying where to write log files, be aware of some security risks which are present if anyone other than the user that starts Apache has write access to the directory where they are written. See the security tips document for details.
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Licensed under the Apache License, Version 2.0.