WIth current glibc's (tested on RHL62 and RHL71), it's pretty safe to
'--with-ipv4-default' from openssh compile-time options.
This makes it so that when you connect like 'ssh some.box' ssh will first
do a AAAA
(IPv6) DNS lookup, and after that fails (~0.1 sec or less), does the normal
Some other vendors have also been enabling this, e.g. Mandrake apparently.
In practise, all this means is you don't have to use 'scp -6' or 'ssh -6'
to ipv6 hosts.
Only apparent side-effect I have noticed (apart from AAAA query), on a box
where there is no IPv6 is:
Jun 26 10:45:23 pajulintu modprobe: modprobe: Can't locate module net-pf-10
when sshd is started. This is good because if there would be 'alias
in /etc/modules.conf, sshd would autoload it which wouldn't be the intent
(the alias is added by initscripts if NETWORKING_IPV6 is set)
This change will be made for 7.x systems in 2.9p2-7 and later. Thanks!