Differ between traceroute/traceroute6

Nice example with traceroute6 but I think it's important to clearify
that there is a traceroute for IPv4 and IPv6. Make in 5-6 years you
can make it more safe "traceroute6" only, but for now its better to
have both. Otherwise people could be confused by the error message if
you do traceroute6 with a IPv4. ;)