Comment 15 for bug 782890

I assume the problem is rather that $Conf{Ping6Path} is not set at all ("undef" means that it is not set) and that hosts have AAAA records, maybe even only AAAA records. From my experience this is though only needed for IPv6-only hosts and not needed for dual-stack hosts. (Which is probably also the reason why it hasn't been added by default.)

The actually required value for $Conf{Ping6Path} might though differ depending on which ping implementation is used:

With legacy inetutils-ping these are still two different binaries and /bin/ping doesn't resolve AAAA records and it needs be set to /bin/ping6.

With modern iputils-ping /bin/ping6 is a (likely transitional) symlink to /bin/ping which I assume will go away somewhen in the future. So in that case it should be set to /bin/ping.

You can set it to /bin/ping6 with iputils-ping, too, but it will break once iputils-ping no more ships the /bin/ping6 symlink.