Name-based virtual hosts allow a web server to host multiple domain names (www.daemons.net, mail.daemons.net, blatch.daemons.net) from one IP address. This allows a web hosting infrastructure to conserve IP address space, and simplify namespace management.
Apache name-based virtual hosts are configured with the “NameVirtualHost” and “VirtualHost” directives, and rely on the HTTP “Host:” header attribute. This attribute is required in HTTP 1.1, and should be present with every request. The following example grabs /index.html using the HTTP/1.1 protocol:
telnet www.daemons.net 80
Trying 126.96.36.199... Connected to www.daemons.net. Escape character is '^]'. GET / HTTP/1.1 Host: www.daemons.net HTTP/1.1 200 OK Date: Thu, 24 Feb 2005 16:33:23TGMT:00-04:00 Server: Apache/2.0.52 Last-Modified: Sun, 20 Jun 2004 14:39:21 GMT ETag: "d54a2-912-c108d840" Accept-Ranges: bytes Content-Length: 2322 Content-Type: text/html [ ... ]
Based on this output, it looks like my friend Clay needs to obscure his “Server:” header. Server identification is controlled with the “ServerTokens” directives.