<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<modulesynopsis>

<name>mod_proxy</name>
<description>HTTP/1.1 proxy/gateway server</description>
<status>Extension</status>
<sourcefile>mod_proxy.c</sourcefile>
<identifier>proxy_module</identifier>

<summary>
<note type="warning"><title>Warning</title>
This document has been updated to take into account changes
made in the 2.0 version of the Apache HTTP Server.  Some of the
information may still be inaccurate, please use it
with care.
</note>

<p>This module implements a proxy/gateway for Apache. It implements
proxying capability for
<code>FTP</code>,
<code>CONNECT</code> (for SSL),
<code>HTTP/0.9</code>,
<code>HTTP/1.0</code>, and
<code>HTTP/1.1</code>.
The module can be configured to connect to other proxy modules for these
and other protocols.</p>

<p>This module was experimental in Apache 1.1.x. Improvements and bugfixes
were made in Apache v1.2.x and Apache v1.3.x, then the module underwent a major
overhaul for Apache v2.0. The protocol support was upgraded to HTTP/1.1,
and filter support was enabled.</p>

<p>Please note that the <strong>caching</strong> function present in
mod_proxy up to Apache v1.3.x has been <strong>removed</strong> from
mod_proxy and will be incorporated into a new module, mod_cache.</p>

<note type="warning"><p>Do not enable proxying with <directive
module="mod_proxy">ProxyRequests</directive> until you have 
<a href="#access">secured your server</a>.  Open proxy servers are
dangerous both to your network and to the Internet at large.</p></note>


</summary>

<section id="configs"><title>Common configuration topics</title>

<ul>
<li><a href="#forwardreverse">Forward and Reverse Proxies</a></li>
<li><a href="#access">Controlling access to your proxy</a></li>
<li><a href="#shortname">Using Netscape hostname shortcuts</a></li>
<li><a href="#mimetypes">Why doesn't file type <em>xxx</em> download via FTP?</a></li>
<li><a href="#type">How can I force an FTP ASCII download of File <em>xxx</em>?</a></li>
<li><a href="#percent2fhack">How can I access FTP files outside of my home directory?</a></li>
<li><a href="#ftppass">How can I hide the FTP cleartext password in my browser's URL line?</a></li>
<li><a href="#startup">Why does Apache start more slowly when using the
        proxy module?</a></li>
<!--<li><a href="#socks">Can I use the Apache proxy module with my SOCKS proxy?</a>-->
<li><a href="#intranet">What other functions are useful for an intranet proxy server?</a></li>
<li><a href="#envsettings">How can I make the proxy talk HTTP/1.0 and disable keepalives?</a></li>
</ul>

<section id="forwardreverse"><title>Forward and Reverse Proxies</title>

<p>Apache can be configured in both a <em>forward</em> and <em>reverse</em>
proxy configuration.</p>

<p>A <em>forward proxy</em> is an intermediate system that enables a browser to connect to a
remote network to which it normally does not have access. A forward proxy
can also be used to cache data, reducing load on the networks between the
forward proxy and the remote webserver.</p>

<p>Apache's mod_proxy can be figured to behave like a forward proxy
using the <directive module="mod_proxy">ProxyRemote</directive>
directive. In addition, caching of data can be achieved by configuring
Apache <module>mod_cache</module>. Other dedicated forward proxy
packages include <a href="http://www.squid.org">Squid</a>.</p>

<p>A <em>reverse proxy</em> is a webserver system that is capable of serving webpages
sourced from other webservers - in addition to webpages on disk or generated
dynamically by CGI - making these pages look like they originated at the
reverse proxy.</p>

<p>When configured with the mod_cache module the reverse
proxy can act as a cache for slower backend webservers. The reverse proxy
can also enable advanced URL strategies and management techniques, allowing
webpages served using different webserver systems or architectures to
coexist inside the same URL space. Reverse proxy systems are also ideal for
implementing centralised logging websites with many or diverse website
backends. Complex multi-tier webserver systems can be constructed using an
Apache mod_proxy frontend and any number of backend webservers.</p>

<p>The reverse proxy is configured using the
<directive module="mod_proxy">ProxyPass</directive> and <directive
module="mod_proxy">ProxyPassReverse</directive> directives. Caching can be
enabled using mod_cache as with the forward proxy.</p>

</section>

<section id="access"><title>Controlling access to your proxy</title>

<p>You can control who can access your proxy via the 
<directive module="mod_proxy" type="section">Proxy</directive>
control block using the following example:</p>

<example>
&lt;Proxy *&gt;<br />
Order Deny,Allow<br />
Deny from all<br />
Allow from 192.168.0<br />
&lt;/Proxy&gt;
</example>

<p>When configuring a reverse proxy, access control takes on the
attributes of the normal server <directive module="core"
type="section">directory</directive> configuration.</p>


<!--<h2><a name="shortname">Using Netscape hostname shortcuts</a></h2>

There is an optional patch to the proxy module to allow Netscape-like
hostname shortcuts to be used. It's available from the
<a href="http://www.apache.org/dist/contrib/patches/1.2/netscapehost.patch"
><code>contrib/patches/1.2</code></a> directory on the Apache Web
site.<p>-->

</section>

<section id="mimetypes"><title>Why doesn't file type <em>xxx</em>
download via FTP?</title>

<p>You probably don't have that particular file type defined as
<em>application/octet-stream</em> in your proxy's mime.types configuration
file. A useful line can be</p>

<example>
application/octet-stream        bin dms lha lzh exe class tgz taz
</example>
</section>

<section id="type"><title>How can I force an FTP ASCII download of
File <em>xxx</em>?</title>

<p>In the rare situation where you must download a specific file using the FTP
<strong>ASCII</strong> transfer method (while the default transfer is in
<strong>binary</strong> mode), you can override mod_proxy's default by
suffixing the request with <code>;type=a</code> to force an ASCII transfer.
(FTP Directory listings are always executed in ASCII mode, however.)</p>
</section>

<section id="percent2fhck"><title>How can I access FTP files outside
of my home directory?</title>

<p>
An FTP URI is interpreted relative to the home directory of the user
who is logging in. Alas, to reach higher directory levels you cannot
use /../, as the dots are interpreted by the browser and not actually
sent to the FTP server. To address this problem, the so called "Squid
%2f hack" was implemented in the Apache FTP proxy; it is is a solution
which is also used by other popular proxy servers like the <a
href="http://www.squid-cache.org/">Squid Proxy Cache</a>.  By
prepending /%2f to the path of your request, you can make such a proxy
change the FTP starting directory to / (instead of the home
directory). </p> 

<p><strong>Example:</strong> To retrieve the file
<code>/etc/motd</code>, you would use the URL</p>
<example>ftp://<em>user@host</em>/%2f/etc/motd</example>
</section>

<section id="ftppass"><title>How can I hide the FTP cleartext password
in my browser's URL line?</title>

<p>
To log in to an FTP server by username and password, Apache
uses different strategies.
In absense of a user name and password in the URL altogether,
Apache sends an anomymous login to the FTP server, i.e.,</p>
<example>
user: anonymous<br />
password: apache_proxy@
</example>
<p>This works for all popular FTP servers which are configured for
anonymous access.</p>

<p>For a personal login with a specific username, you can embed
the user name into the URL, like in:
<code>ftp://<em>username@host</em>/myfile</code>. If the FTP server
asks for a password when given this username (which it should),
then Apache will reply with a [401 Authorization required] response,
which causes the Browser to pop up the username/password dialog.
Upon entering the password, the connection attempt is retried,
and if successful, the requested resource is presented.
The advantage of this procedure is that your browser does not
display the password in cleartext (which it would if you had used
<code>ftp://<em>username:password@host</em>/myfile</code> in
the first place).</p>

<note><title>Note</title>
The password which is transmitted in such a way
is not encrypted on its way. It travels between your browser and
the Apache proxy server in a base64-encoded cleartext string, and
between the Apache proxy and the FTP server as plaintext. You should
therefore think twice before accessing your FTP server via HTTP
(or before accessing your personal files via FTP at all!) When
using unsecure channels, an eavesdropper might intercept your
password on its way.
</note>
</section>

<section id="startup"><title>Why does Apache start more slowly when
using the proxy module?</title>

<p>If you're using the <directive module="mod_proxy">ProxyBlock</directive>
directive, hostnames' IP addresses are looked up and cached during
startup for later match test. This may take a few seconds (or more)
depending on the speed with which the hostname lookups occur.</p>
</section>

<!--<h2><a name="socks">Can I use the Apache proxy module with my SOCKS proxy?</a></h2>

Yes. Just build Apache with the rule <code>SOCKS4=yes</code> in your
<em>Configuration</em> file, and follow the instructions there. SOCKS5
capability can be added in a similar way (there's no <code>SOCKS5</code>
rule yet), so use the <code>EXTRA_LDFLAGS</code> definition, or build Apache
normally and run it with the <em>runsocks</em> wrapper provided with SOCKS5,
if your OS supports dynamically linked libraries.<p>

Some users have reported problems when using SOCKS version 4.2 on Solaris.
The problem was solved by upgrading to SOCKS 4.3.<p>

Remember that you'll also have to grant access to your Apache proxy machine by
permitting connections on the appropriate ports in your SOCKS daemon's
configuration.<p>
-->

<section id="intranet"><title>What other functions are useful for an
intranet proxy server?</title>

<p>An Apache proxy server situated in an intranet needs to forward
external requests through the company's firewall. However, when it has
to access resources within the intranet, it can bypass the firewall
when accessing hosts. The <directive
module="mod_proxy">NoProxy</directive> directive is useful for
specifying which hosts belong to the intranet and should be accessed
directly.</p>

<p>Users within an intranet tend to omit the local domain name from their
WWW requests, thus requesting "http://somehost/" instead of
"http://somehost.my.dom.ain/". Some commercial proxy servers let them get
away with this and simply serve the request, implying a configured
local domain. When the <directive module="mod_proxy">ProxyDomain</directive> directive
is used and the server is <a href="#proxyrequests">configured for
proxy service</a>, Apache can return a redirect response and send the client
to the correct, fully qualified, server address. This is the preferred method
since the user's bookmark files will then contain fully qualified hosts.</p>
</section>
<section id="envsettings"><title>How can I make the proxy talk HTTP/1.0 and 
disable keepalives?</title>

<p>For circumstances where you have a application server which doesn't implement
keepalives or HTTP/1.1 properly, there are 2 environment variables which when
set send a HTTP/1.0 with no keepalive. These are set via the  <directive
module="mod_env">SetEnv</directive> directive.</p>
<p>These are the 'force-proxy-request-1.0' and 'proxy-nokeepalive' notes.</p>

<example>
&lt;location /buggyappserver/ &gt;<br />
ProxyPass http://buggyappserver:7001/foo/<br />
SetEnv force-proxy-request-1.0 1<br />
SetEnv proxy-nokeepalive 1<br />
&lt;/location&gt;
</example>

</section>

</section>

<directivesynopsis type="section">
<name>Proxy</name>
<syntax>&lt;Proxy <em>wildcard-url</em>&gt; ...&lt;/Proxy&gt;</syntax>
<description>Container for directives applied to proxied 
resources</description>
<contextlist><context>server config</context>
<context>virtual host</context></contextlist>

<usage>
<p>Directives placed in <directive type="section">Proxy</directive>
sections apply only to matching proxied content.  Shell-style
wildcards are allowed.</p>

<p>For example, the following will allow only hosts in
<code>yournetwork.example.com</code> to access content via your
proxy server:</p>

<example>
&lt;Proxy *&gt;<br />
&nbsp;&nbsp;Order Deny,Allow<br />
&nbsp;&nbsp;Deny from all<br />
&nbsp;&nbsp;Allow from yournetwork.example.com<br />
&lt;/Proxy&gt;
</example>

<p>The following example will process all files in the
<code>foo</code> directory of <code>example.com</code> through the
<code>INCLUDES</code> filter when they are sent through the proxy
server:</p>
<example>
&lt;Proxy http://example.com/foo/*&gt;<br />
&nbsp;&nbsp;SetOutputFilter INCLUDES<br />
&lt;/Proxy&gt;
</example>
</usage>
</directivesynopsis>


<directivesynopsis type="section">
<name>ProxyMatch</name>
<syntax>&lt;Proxy <em>regex</em>&gt; ...&lt;/Proxy&gt;</syntax>
<description>Container for directives applied to regular-expression-matched 
proxied resources</description>
<contextlist><context>server config</context>
<context>virtual host</context></contextlist>

<usage>
<p>The <directive type="section">ProxyMatch</directive> directive is
identical to the <directive module="mod_proxy"
type="section">Proxy</directive> directive, except it matches URLs
using regular expressions.</p>
</usage>
</directivesynopsis>


<directivesynopsis>
<name>ProxyPreserveHost</name>
<description>Use incoming Host HTTP request header for
proxy request</description>
<syntax>ProxyPreserveHost on|off</syntax>
<default>ProxyPreserveHost Off</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>
<compatibility>Available in
Apache 2.0.31 and later.</compatibility>

<usage>
<p>When enabled, this option will pass the Host: line from the
incoming request to the proxied host, instead of the hostname
specified in the proxypass line.
</p>
<p>This option should normally be turned 'off'.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyRequests</name>
<description>Enables forward (standard) proxy requests</description>
<syntax>ProxyRequests on|off</syntax>
<default>ProxyRequests Off</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>This allows or prevents Apache from functioning as a forward proxy
server. (Setting ProxyRequests to 'off' does not disable use of the 
<directive module="mod_proxy">ProxyPass</directive> directive.)</p>

<p>In a typical reverse proxy configuration, this option should be set to
'off'.</p>

<note type="warning"><p>Do not enable proxying with <directive
module="mod_proxy">ProxyRequests</directive> until you have 
<a href="#access">secured your server</a>.  Open proxy servers are
dangerous both to your network and to the Internet at large.</p></note>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyRemote</name>
<description>Remote proxy used to handle certain requests</description>
<syntax>ProxyRemote <em>match remote-server</em></syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>This defines remote proxies to this proxy. <em>match</em> is either the
name of a URL-scheme that the remote server supports, or a partial URL
for which the remote server should be used, or '*' to indicate the
server should be contacted for all requests. <em>remote-server</em> is a
partial URL for the remote server. Syntax:</p>

<pre>
  remote-server = protocol://hostname[:port]
</pre>

<p><em>protocol</em> is the protocol that should be used to communicate
with the remote server; only "http" is supported by this module.</p>

<p>
Example:</p>
<example>
  ProxyRemote http://goodguys.com/ http://mirrorguys.com:8000<br />
  ProxyRemote * http://cleversite.com<br />
  ProxyRemote ftp http://ftpproxy.mydomain.com:8080
</example>

<p>In the last example, the proxy will forward FTP requests, encapsulated
as yet another HTTP proxy request, to another proxy which can handle
them.</p>

<p>This option also supports reverse proxy configuration - a backend
webserver can be embedded within a virtualhost URL space even if that
server is hidden by another forward proxy.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyRemoteMatch</name>
<description>Remote proxy used to handle requests
matched by regular expressions</description>
<syntax>ProxyRemote <em>regex remote-server</em></syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>The <directive>ProxyRemoteMatch</directive> is identical
to the <directive module="mod_proxy">ProxyRemote</directive>
directive, except the first argument is a regular expression
match against the requested URL.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyPass</name>
<description>Maps remote servers into the local server 
URL-space</description>
<syntax>ProxyPass [<em>path</em>] !|<em>url</em></syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>This directive allows remote servers to be mapped into the space of
the local server; the local server does not act as a proxy in the
conventional sense, but appears to be a mirror of the remote
server. <em>path</em> is the name of a local virtual path;
<em>url</em> is a partial URL for the remote server and cannot
include a query string.</p>

<p>Suppose the local server has address <code>http://wibble.org/</code>; 
then</p>
<example>
   ProxyPass /mirror/foo/ http://foo.com/
</example>
<p>will cause a local request for the
&lt;<code>http://wibble.org/mirror/foo/bar</code>&gt; to be
internally converted into a proxy request to
&lt;<code>http://foo.com/bar</code>&gt;.</p>
<p>
The ! directive is useful in situations where you don't want to reverse-proxy
a subdirectory. eg.</p>
<example>
        ProxyPass /mirror/foo/i !<br />
        ProxyPass /mirror/foo http://foo.com
</example>
<p>will proxy all requests to /mirror/foo to foo.com EXCEPT requests made to /mirror/foo/i</p>

<note>NB: order is important. you need to put the exclusions BEFORE the general proxypass directive</note>

<p>When used inside a <directive type="section"
module="core">Location</directive> section, the first argument is
ommitted and the local directory is obtained from the <directive
type="section" module="core">Location</directive>.</p>

<p>If you require a more flexible reverse-proxy configuration, see
the <directive module="mod_rewrite">RewriteRule</directive> directive
with the <code>[P]</code> flag.</p>

</usage>

</directivesynopsis>

<directivesynopsis>
<name>ProxyPassReverse</name>
<description>Adjusts the URL in HTTP response headers sent from
a reverse proxied server</description>
<syntax>ProxyPassReverse [<em>path</em>] <em>url</em></syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>This directive lets Apache adjust the URL in the <code>Location</code>,
<code>Content-Location</code> and <code>URI</code> headers on
HTTP redirect responses. This is essential when Apache is used as
a reverse proxy to avoid by-passing the reverse proxy because of HTTP
redirects on the backend servers which stay behind the reverse proxy.</p>

<p><em>path</em> is the name of a local virtual path.<br />
<em>url</em> is a partial URL for the remote server - the same way they are
used for the <directive module="mod_proxy">ProxyPass</directive> directive.</p>

<p>
Example:<br />
Suppose the local server has address <code>http://wibble.org/</code>; then</p>
<example>
   ProxyPass         /mirror/foo/ http://foo.com/<br />
   ProxyPassReverse  /mirror/foo/ http://foo.com/
</example>
<p>will not only cause a local request for the
&lt;<code>http://wibble.org/mirror/foo/bar</code>&gt; to be internally
converted into a proxy request to &lt;<code>http://foo.com/bar</code>&gt; (the
functionality <code>ProxyPass</code> provides here). It also takes care of
redirects the server foo.com sends: when <code>http://foo.com/bar</code> is
redirected by him to <code>http://foo.com/quux</code> Apache adjusts this to
<code>http://wibble.org/mirror/foo/quux</code> before forwarding the HTTP
redirect response to the client. </p>
<p>
Note that this <directive>ProxyPassReverse</directive> directive can
also be used in conjunction with the proxy pass-through feature
("<code>RewriteRule ...  [P]</code>") from
<module>mod_rewrite</module> because its doesn't depend on a
corresponding <directive module="mod_proxy">ProxyPass</directive>
directive.</p>

<p>When used inside a <directive type="section"
module="core">Location</directive> section, the first argument is
ommitted and the local directory is obtained from the <directive
type="section" module="core">Location</directive>.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>AllowCONNECT</name>
<description>Ports that are allowed to <code>CONNECT</code> through
the proxy</description>
<syntax>AllowCONNECT <em>port</em> [<em>port</em>] ...</syntax>
<default>AllowCONNECT 443 563</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>The <directive>AllowCONNECT</directive> directive specifies a list
of port numbers to which the proxy <code>CONNECT</code> method may
connect.  Today's browsers use this method when a <em>https</em>
connection is requested and proxy tunneling over <em>http</em> is in
effect.<br /> By default, only the default https port (443) and the
default snews port (563) are enabled. Use the
<directive>AllowCONNECT</directive> directive to overrride this default and
allow connections to the listed ports only.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyBlock</name>
<description>Words, hosts, or domains that are banned from being
proxied</description>
<syntax>ProxyBlock *|<em>word|host|domain</em>
[<em>word|host|domain</em>] ...</syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>The <directive>ProxyBlock</directive> directive specifies a list of
words, hosts and/or domains, separated by spaces.  HTTP, HTTPS, and
FTP document requests to sites whose names contain matched words,
hosts or domains are <em>blocked</em> by the proxy server. The proxy
module will also attempt to determine IP addresses of list items which
may be hostnames during startup, and cache them for match test as
well. Example:</p>

<example>
  ProxyBlock joes-garage.com some-host.co.uk rocky.wotsamattau.edu
</example>

<p>'rocky.wotsamattau.edu' would also be matched if referenced by IP
address.</p>

<p>Note that 'wotsamattau' would also be sufficient to match
'wotsamattau.edu'.</p>

<p>Note also that</p>

<example>
ProxyBlock *
</example>

<p>blocks connections to all sites.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyReceiveBufferSize</name>
<description>Network buffer size for outgoing HTTP and FTP 
connections</description>
<syntax>ProxyReceiveBufferSize <em>bytes</em></syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>The <directive>ProxyReceiveBufferSize</directive> directive
specifies an explicit network buffer size for outgoing HTTP and FTP
connections, for increased throughput.  It has to be greater than 512
or set to 0 to indicate that the system's default buffer size should
be used.</p>
<example><title>Example</title>
  ProxyReceiveBufferSize 2048
</example>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyIOBufferSize</name>
<description>IO buffer size for outgoing HTTP and FTP 
connections</description>
<syntax>ProxyIOBufferSize <em>bytes</em></syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<!-- XXX: content needed -->
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyMaxForwards</name>
<description>Maximium number of proxies that a request can be forwarded
through</description>
<syntax>ProxyMaxForwards <em>number</em></syntax>
<default>ProxyMaxForwards 10</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>
<compatibility>Available in Apache 2.0 and later</compatibility>

<usage>
<p>The <directive>ProxyMaxForwards</directive> directive specifies the
maximum number of proxies through which a request may pass. This is
set to prevent infinite proxy loops, or a DoS attack.</p>

<example><title>Example</title>
  ProxyMaxForwards 10
</example>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>NoProxy</name>
<description>Hosts, domains, or networks that will be connected
to directly</description>
<syntax>NoProxy 
 <em>Domain</em>|
 <em>SubNet</em>|
 <em>IpAddr</em>| 
 <em>Hostname</em>
[<em>Domain</em>| 
 <em>SubNet</em>|
 <em>IpAddr</em>| 
 <em>Hostname</em>] ...</syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>This directive is only useful for Apache proxy servers within
intranets.  The <directive>NoProxy</directive> directive specifies a
list of subnets, IP addresses, hosts and/or domains, separated by
spaces. A request to a host which matches one or more of these is
always served directly, without forwarding to the configured
<directive module="mod_proxy">ProxyRemote</directive> proxy server(s).</p>

<example><title>Example</title>
  ProxyRemote  *  http://firewall.mycompany.com:81<br />
  NoProxy         .mycompany.com 192.168.112.0/21 
</example>

<p>The arguments to the NoProxy directive are one of the following type list:</p>
   <dl>
    <!-- ===================== Domain ======================= -->
    <dt><a name="domain">
    <em>Domain</em></a></dt>
    <dd>A <em>Domain</em> is a partially qualified DNS domain name, preceded
        by a period.
        It represents a list of hosts which logically belong to the same DNS
        domain or zone (<em>i.e.</em>, the suffixes of the hostnames are all ending in 
        <em>Domain</em>).<br />
		Examples: <code>.com</code>   <code>.apache.org.</code><br />
        To distinguish <em>Domain</em>s from <a href="#hostname"><em>Hostname</em></a>s (both
        syntactically and semantically; a DNS domain can have a DNS A record,
        too!), <em>Domain</em>s are always written
        with a leading period.<br />
        Note: Domain name comparisons are done without regard to the case,
        and <em>Domain</em>s are always assumed to be anchored in the root 
        of the DNS tree, therefore two domains <code>.MyDomain.com</code> and
        <code>.mydomain.com.</code> (note the trailing period) are
        considered equal. Since a domain comparison does not involve a DNS
	lookup, it is much more efficient than subnet comparison.</dd>

    <!-- ===================== SubNet ======================= -->
    <dt><a name="subnet">
    <em>SubNet</em></a></dt>
    <dd>A <em>SubNet</em> is a partially qualified internet address in
        numeric (dotted quad) form, optionally followed by a slash and the
        netmask, specified as the number of significant bits in the
        <em>SubNet</em>. It is used to represent a subnet of hosts which can
        be reached over a common network interface. In the absence of the
        explicit net mask it is assumed that omitted (or zero valued)
        trailing digits specify the mask. (In this case, the netmask can
        only be multiples of 8 bits wide.)<br />
        Examples:
        <dl>
         <dt><code>192.168</code> or <code>192.168.0.0</code></dt>
         <dd>the subnet 192.168.0.0 with an implied netmask of 16 valid bits
             (sometimes used in the netmask form <code>255.255.0.0</code>)</dd>
         <dt><code>192.168.112.0/21</code></dt>
         <dd>the subnet <code>192.168.112.0/21</code> with a netmask of 21
             valid bits (also used in the form 255.255.248.0)</dd>
        </dl>
	As a degenerate case, a <em>SubNet</em> with 32 valid bits is the
        equivalent to an <em>IPAddr</em>, while a <em>SubNet</em> with zero
        valid bits (<em>e.g.</em>, 0.0.0.0/0) is the same as the constant
        <em>_Default_</em>, matching any IP address. </dd>

    <!-- ===================== IPAddr ======================= -->
    <dt><a name="ipaddr">
    <em>IPAddr</em></a></dt>
    <dd>A <em>IPAddr</em> represents a fully qualified internet address in
        numeric (dotted quad) form. Usually, this address represents a
        host, but there need not necessarily be a DNS domain name
        connected with the address.<br />
		Example: 192.168.123.7<br />
        Note: An <em>IPAddr</em> does not need to be resolved by the DNS
	system, so it can result in more effective apache performance.</dd>

    <!-- ===================== Hostname ======================= -->
    <dt><a name="hostname">
    <em>Hostname</em></a></dt>
    <dd>A <em>Hostname</em> is a fully qualified DNS domain name which can
        be resolved to one or more <a
	href="#ipaddr"><em>IPAddrs</em></a> via the DNS domain name service. 
        It represents a logical host (in contrast to
	<a href="#domain"><em>Domain</em></a>s, see 
        above) and must be resolvable to at least one <a
	href="#ipaddr"><em>IPAddr</em></a> (or often to a list of hosts
	with different <a href="#ipaddr"><em>IPAddr</em></a>'s).<br /> 
		Examples: <code>prep.ai.mit.edu</code>
                  <code>www.apache.org.</code><br />
        Note: In many situations, it is more effective to specify an
        <a href="#ipaddr"><em>IPAddr</em></a> in place of a
	<em>Hostname</em> since a DNS lookup 
        can be avoided. Name resolution in Apache can take a remarkable deal
        of time when the connection to the name server uses a slow PPP
        link.<br />
        Note: <em>Hostname</em> comparisons are done without regard to the case,
        and <em>Hostname</em>s are always assumed to be anchored in the root
        of the DNS tree, therefore two hosts <code>WWW.MyDomain.com</code>
        and <code>www.mydomain.com.</code> (note the trailing period) are
        considered equal.</dd>
</dl>
</usage>
<seealso><a href="../dns-caveats.html">DNS Issues</a></seealso>
</directivesynopsis>

<directivesynopsis>
<name>ProxyTimeout</name>
<description>Network timeout for proxied requests</description>
<syntax>ProxyTimeout <em>seconds</em></syntax>
<default>ProxyTimeout 300</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>
<compatibility>Available in
Apache 2.0.31 and later</compatibility>

<usage>
<p>This directive allows a user to specifiy a timeout on proxy requests.
This is usefull when you have a slow/buggy appserver which hangs,
and you would rather just return a timeout and fail gracefully instead
of waiting however long it takes the server to return
</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyDomain</name>
<description>Default domain name for proxied requests</description>
<syntax>ProxyDomain <em>Domain</em></syntax>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>This directive is only useful for Apache proxy servers within
intranets.  The <directive>ProxyDomain</directive> directive specifies
the default domain which the apache proxy server will belong to. If a
request to a host without a domain name is encountered, a redirection
response to the same host with the configured <em>Domain</em> appended
will be generated.</p>

<example><title>Example</title>
  ProxyRemote  *  http://firewall.mycompany.com:81<br />
  NoProxy         .mycompany.com 192.168.112.0/21<br />
  ProxyDomain     .mycompany.com
</example>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyVia</name>
<description>Information provided in the <code>Via</code> HTTP response
header for proxied requests</description>
<syntax>ProxyVia on|off|full|block</syntax>
<default>ProxyVia off</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>

<usage>
<p>This directive controls the use of the <code>Via:</code> HTTP
header by the proxy. Its intended use is to control the flow of of
proxy requests along a chain of proxy servers.  See RFC2068 (HTTP/1.1)
for an explanation of <code>Via:</code> header lines.</p>

<ul> <li>If set
to <em>off</em>, which is the default, no special processing is
performed. If a request or reply contains a <code>Via:</code> header,
it is passed through unchanged.</li>

<li>If set to <em>on</em>, each
request and reply will get a <code>Via:</code> header line added for
the current host.</li>

<li>If set to <em>full</em>, each generated <code>Via:</code> header
line will additionally have the Apache server version shown as a
<code>Via:</code> comment field.</li>

<li>If set to <em>block</em>, every
proxy request will have all its <code>Via:</code> header lines
removed. No new <code>Via:</code> header will be generated.</li>
</ul>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ProxyErrorOverride</name>
<description>Override error pages for proxied content</description>
<syntax>ProxyErrorOverride On|Off</syntax>
<default>ProxyErrorOverride Off</default>
<contextlist><context>server config</context>
<context>virtual host</context>
</contextlist>
<compatibility>Available in version 2.0 and later</compatibility>

<usage>
<p>This directive is useful for reverse-proxy setups, where you want to 
have a common look and feel on the error pages seen by the end user. 
This also allows for included files (via mod_include's SSI) to get
the error code and act accordingly (default behavior would display
the error page of the proxied server, turning this on shows the SSI
Error message).</p>
</usage>
</directivesynopsis>


</modulesynopsis>
