Which version of INN supports IPv6?

You should use INN version 2.4.x, however it is recommeded to use 2.4.1 at least, since earlier version has some vulnerabilities.

How can enable IPv6 support in INN?

IPv6 support must explicitly enabled with the --enable-ipv6 flag to the configure script, then compile and install according to your local policy.

Which components of INN has IPv6 support?

There is IPv6 support to innd and inndstart, auth_pass, nnrpd, innfeed, and the ident auth program, but there is no IPv6 support for imapfeed and other auxiliary programs like the radius auth backend.

What I have to change if I want IPv6 support?

Things that will break if you compile with --enable-ipv6:

innd can only be started via inndstart
IP_OPTIONS are not cleared for any incoming connections to innd even over IPv4

If you are using ident, identd contacts the remote host using either IPv4 or IPv6 depending on which protocol was used for the incoming NNTP connection.

What can I configure for IPv6 in inn.conf?

You can configure several parameters in inn.conf(5)

bindaddress6 The IPv6 local address used by INN. If only one of the bindaddress and bindaddress6 parameters is used, then only the socket for the corresponding address family is created. If both parameters are used then two sockets are created. If neither of them is used, the list of sockets to listen on will be determined by the system library getaddrinfo(3) function. The value of the INND_BIND_ADDRESS6, if set, overrides this setting. Note that you will generally need to put double quotes ("") around this value if you set it, since IPv6 addresses contain colons.
sourceaddress6 Which local IPv6 address to bind to for outgoing NNTP sockets.

What can I configure for IPv6 in innfeed.conf?

You can configure some parameters in innfeed.conf(5)

bindaddress6 The IPv6 local address used by innfeed outgoing connections.

How should I start nnrpd?

You can start nnrpd NNTP server to serve local users via IPv6 -b address option. The <tt>-b</tt> parameter instructs nnrpd to bind to the specified IP address when started as a standalone daemon using the -D flag. This has to be a valid IPv4 or IPv6 address belonging to an interface of the local host. It can also be ::0 (although the default is 0.0.0.0 if unspecified). Of course you can start nnrpd from inetd/xinetd also, and if your inetd/xinetd support IPv6 you can provide News via IPv6 to your local users.