Special IPv6 Considerations

Special IPv6 Considerations -

When APR supports IPv6, Apache will create IPv6-capable listening - sockets by default (i.e., when no IP address is specified on the - Listen directive). In other words, when APR supports IPv6,

A growing number of platforms implement IPv6, and APR supports + IPv6 on most of these platforms, allowing Apache to allocate IPv6 + sockets and handle requests which were sent over IPv6.

+ +

One complicating factor for Apache administrators is whether or + not an IPv6 socket can handle both IPv4 connections and IPv6 + connections. Handling IPv4 connections with an IPv6 socket uses + IPv4-mapped IPv6 addresses, which are allowed by default on most + platforms but are disallowed by default on FreeBSD, NetBSD, and + OpenBSD in order to match the system-wide policy on those + platforms. But even on systems where it is disallowed by default, a + special configure parameter can change this behavior for Apache.

+ +

If you want Apache to handle IPv4 and IPv6 connections with a + minimum of sockets, which requires using IPv4-mapped IPv6 addresses, + specify the --enable-v4-mapped configure option and use + generic Listen directives like the following:

Listen 80 -

is equivalent to

With --enable-v4-mapped, the Listen directives in the + default configuration file created by Apache will use this form. + --enable-v4-mapped is the default on all platforms but + FreeBSD, NetBSD, and OpenBSD, so this is probably how your Apache was + built.

+ +

If you want Apache to handle IPv4 connections only, regardless of + what your platform and APR will support, specify an IPv4 address on all + Listen directives, as in the following examples:

- Listen [::]:80 - - -

When APR does not support IPv6,

- - - Listen 80 + Listen 0.0.0.0:80 + Listen 192.170.2.1:80 -

is equivalent to

If you want Apache to handle IPv4 and IPv6 connections on separate + sockets (i.e., to disable IPv4-mapped addresses), specify the + --disable-v4-mapped configure option and use specific Listen + directives like the following:

+ Listen [::]:80 Listen 0.0.0.0:80 -

On some platforms, such as NetBSD, binding to the IPv6 wildcard address - ("::") does not allow Apache to accept connections on IPv4 interfaces. - In this situation, multiple Listen directives are required, as shown - below:

- - - Listen 0.0.0.0:80
- Listen [::]:0 - +

With --disable-v4-mapped, the Listen directives in the + default configuration file created by Apache will use this form. + --disable-v4-mapped is the default on FreeBSD, NetBSD, and + OpenBSD.

Apache does not currently detect this, so the Listen statements must - be edited manually by the administrator.

1.29 +37 -23 httpd-2.0/docs/manual/bind.html.en Index: bind.html.en =================================================================== RCS file: /home/cvs/httpd-2.0/docs/manual/bind.html.en,v retrieving revision 1.28 retrieving revision 1.29 diff -u -r1.28 -r1.29 --- bind.html.en 11 Dec 2002 21:33:36 -0000 1.28 +++ bind.html.en 14 Feb 2003 13:39:43 -0000 1.29 @@ -79,44 +79,58 @@