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23 <manualpage metafile="bind.xml.meta">
25 <title>Binding</title>
28 <p>Configuring Apache to listen on specific addresses and ports.</p>
31 <seealso><a href="vhosts/">Virtual Hosts</a></seealso>
32 <seealso><a href="dns-caveats.html">DNS Issues</a></seealso>
34 <section id="overview">
35 <title>Overview</title>
40 <module>mpm_common</module>
43 <directive module="core" type="section">VirtualHost</directive>
44 <directive module="mpm_common">Listen</directive>
49 <p>When Apache starts, it binds to some port and address on
50 the local machine and waits for incoming requests. By default,
51 it listens to all addresses on the machine. However, it may need to
52 be told to listen on specific ports, or only on selected
53 addresses, or a combination of both. This is often combined with the
54 Virtual Host feature, which determines how Apache responds to
55 different IP addresses, hostnames and ports.</p>
57 <p>The <directive module="mpm_common">Listen</directive>
58 directive tells the server to accept
59 incoming requests only on the specified ports or
60 address-and-port combinations. If only a port number is
61 specified in the <directive module="mpm_common">Listen</directive>
63 listens to the given port on all interfaces. If an IP address
64 is given as well as a port, the server will listen on the given
65 port and interface. Multiple <directive
66 module="mpm_common">Listen</directive> directives may be used to
67 specify a number of addresses and ports to listen on. The
68 server will respond to requests from any of the listed
69 addresses and ports.</p>
71 <p>For example, to make the server accept connections on both
72 port 80 and port 8000, on all interfaces, use:</p>
79 <p>To make the server accept connections on port 80 for one interface,
80 and port 8000 on another, use</p>
83 Listen 192.0.2.1:80<br />
87 <p>IPv6 addresses must be enclosed in square brackets, as in the
88 following example:</p>
91 Listen [2001:db8::a00:20ff:fea7:ccea]:80
96 <title>Special IPv6 Considerations</title>
98 <p>A growing number of platforms implement IPv6, and
99 <glossary>APR</glossary> supports IPv6 on most of these platforms,
100 allowing Apache to allocate IPv6 sockets, and to handle requests sent
103 <p>One complicating factor for Apache administrators is whether or
104 not an IPv6 socket can handle both IPv4 connections and IPv6
105 connections. Handling IPv4 connections with an IPv6 socket uses
106 IPv4-mapped IPv6 addresses, which are allowed by default on most
107 platforms, but are disallowed by default on FreeBSD, NetBSD, and
108 OpenBSD, in order to match the system-wide policy on those
109 platforms. On systems where it is disallowed by default, a
110 special <program>configure</program> parameter can change this behavior
113 <p>On the other hand, on some platforms, such as Linux and Tru64, the
114 <strong>only</strong> way to handle both IPv6 and IPv4 is to use
115 mapped addresses. If you want Apache to handle IPv4 and IPv6 connections
116 with a minimum of sockets, which requires using IPv4-mapped IPv6
117 addresses, specify the <code>--enable-v4-mapped</code> <program>
118 configure</program> option.</p>
120 <p><code>--enable-v4-mapped</code> is the default on all platforms except
121 FreeBSD, NetBSD, and OpenBSD, so this is probably how your Apache was
124 <p>If you want Apache to handle IPv4 connections only, regardless of
125 what your platform and APR will support, specify an IPv4 address on all
126 <directive module="mpm_common">Listen</directive> directives, as in the
127 following examples:</p>
130 Listen 0.0.0.0:80<br />
134 <p>If your platform supports it and you want Apache to handle IPv4 and
135 IPv6 connections on separate sockets (i.e., to disable IPv4-mapped
136 addresses), specify the <code>--disable-v4-mapped</code> <program>
137 configure</program> option. <code>--disable-v4-mapped</code> is the
138 default on FreeBSD, NetBSD, and OpenBSD.</p>
141 <section id="virtualhost">
142 <title>How This Works With Virtual Hosts</title>
145 module="mpm_common">Listen</directive> directive does not implement
146 Virtual Hosts - it only tells the
147 main server what addresses and ports to listen on. If no
148 <directive module="core" type="section">VirtualHost</directive>
149 directives are used, the server will behave
150 in the same way for all accepted requests. However,
151 <directive module="core" type="section">VirtualHost</directive>
152 can be used to specify a different behavior
153 for one or more of the addresses or ports. To implement a
154 VirtualHost, the server must first be told to listen to the
155 address and port to be used. Then a
156 <directive module="core" type="section">VirtualHost</directive> section
157 should be created for the specified address and port to set the
158 behavior of this virtual host. Note that if the
159 <directive module="core" type="section">VirtualHost</directive>
160 is set for an address and port that the
161 server is not listening to, it cannot be accessed.</p>