Apache Reference: mod_proxy, ProxyVia

ProxyVia

Control the Use of the HTTP Via Header Field for the Proxy
Syntax: ProxyVia off|on|full|block
Example: ProxyVia full
Since: Apache 1.3

This directive controls the use of the HTTP Via header field by the proxy server, thereby managing the flow of proxy requests along a chain of proxy servers. See RFC 2068 (HTTP/1.1) for an explanation of Via header fields. If set to ``off'' (the default), no special processing is performed. If a request or reply then contains a Via header field, it passes through unchanged. If set to ``on'', however, a via header field will be added to each request and response for the current proxy server. If set to ``full'', each generated Via header field will have the Apache server version shown as a Via comment field. If set to ``block'', every proxy request will have all its Via header fields removed and no new Via header field will be generated.