Comment 8 for bug 555210

Gro-Tsen,

native IPv6 is still preferred over native IPv4 in Lucid, as it always has. What changed in Lucid is that non-native IPv6 (6to4 and Teredo), is now always less preferred than native IPv4 (even when behind a NAT). I can assure you that having better and more reliable connectivity through 6to4/Teredo than through IPv4 is not typical

Your suggested change is correct, uncommenting those lines in /etc/gai.conf will revert back to the pre-Lucid behaviour where non-native IPv6 will be preferred over IPv4. It should not have any other consequences, no. You can confirm how the getaddrinfo() algorithm sorts the available addresses by using e.g. "getent ahosts www.ripe.net" - the address first listed will be the preferred one.

Tore