Editing Virtual hosting (section)

{{Short description|Hosting of multiple domain names on one server}}
{{about|virtual domain name hosting|virtual machine hosting|host machine}}
{{Distinguish|Virtual private  server}}
{{More citations needed|date=March 2016}}
'''Virtual hosting''' is a method for hosting multiple [[domain name]]s (with separate handling of each name) on a single [[Server (computing)|server]] (or pool of servers).<ref>{{cite web |url= https://www.netcraft.com/active-sites/ |title= How many active sites are there? |access-date = 14 July 2018 |website= [[Netcraft]] |language = en |quote= Circa 1996-1997, the number of distinct IP addresses would have been a good approximation to the number of real sites, since hosting companies would typically allocate an IP address to each site with distinct content, and multiple domain names could point to the IP address being used to serve the same site content. However, with the adoption of HTTP/1.1 virtual hosting, and the availability of load balancing technology it is possible to reliably host a great number of active sites on a single (or relatively few) IP addresses. |archive-url= https://web.archive.org/web/20130430231657/https://www.netcraft.com/active-sites/ |archive-date= 30 April 2013 }}</ref> This allows one server to share its resources, such as memory and processor cycles, without requiring all services provided to use the same host name. The term virtual hosting is usually used in reference to [[web server]]s but the principles do carry over to other [[Internet]] services.

One widely used application is [[Shared web hosting service|shared web hosting]]. The price for shared web hosting is lower than for a dedicated [[web server]] because many customers can be hosted on a single server. It is also very common for a single entity to want to use multiple names on the same machine so that the names can reflect services offered rather than where those services happen to be hosted.

There are two main types of virtual hosting, name-based and IP-based. Name-based virtual hosting uses the host name presented by the client. This saves IP addresses and the associated administrative overhead but the protocol being served must supply the host name at an appropriate point. In particular, there are significant difficulties using name-based virtual hosting with [[transport layer security|SSL/TLS]]. IP-based virtual hosting uses a separate [[IP address]] for each host name, and it can be performed with any protocol but requires a dedicated IP address per domain name served. Port-based virtual hosting is also possible in principle but is rarely used in practice because it is unfriendly to users.

Name-based and IP-based virtual hosting can be combined: a server may have multiple IP addresses and serve multiple names on some or all of those IP addresses. This technique can be useful when using SSL/TLS with wildcard certificates. For example, if a server operator had two certificates, one for *.example.com and one for *.example.net, the operator could serve foo.example.com and bar.example.com off the same IP address but would need a separate IP address for baz.example.net.