I was surprised to see that wget chose to use IPv4 over IPv6 when downloading a file. It looks like it is on purpose (I would call it a bad design choice). You can tell wget to prefer IPv6 over IPv4 by putting the following line
prefer-family = IPv6
in either /etc/wgetrc (system wide) or $HOME/.wgetrc (user settings).
Related posts:
The main reason would be that brain-dead OSes (Linux, for example), will try an IPv6 connection if the destination node has an AAAA DNS record, which will fail in most cases for clients not connected to an IPv6 network (which is still the huge majority of cases). Then you have to wait for the standard TCP timeout in case of a TCP connection, before falling back to IPv4. This gives a bad impression of Linux as having “slow” networking.
> will try an IPv6 connection if the destination node has an AAAA DNS record
Do note that, besides a few obvious cases (no local IPv6 address, only link-local IPv6 addresses, etc), it may be difficult to know if a IPv6 address is reachable or not. You have to try, since there is no global sysctl parameter saying “net.ipv6.use_it=1″.
PS: and it is not Linux, NetBSD has a similar issue.
Practical rule: do not configure global IPv6 addresses if you do not have IPv6 connectivity.
It’s not quite a question of having global IPv6 address, it’s a question of having the machine configured with a IPv6 route to the destination. If connect(2) immediately returns EHOSTUNREACH or ENETUNREACH, there’s absolutely no problem. That’s what happens on FreeBSD. I don’t know about exactly what Linux does. I do agree with Sam, the default wget behaviour is a bad design choice.
A few days ago I tried to update some FreeBSD ports from my IPv6-connected FreeBSD machine, and seeing fetch(1) timeout after successfully establishing IPv6 ftp connections gave me a clue that my IPv6 filters were not set correctly (they didn’t let “icmp6 packet too big” through, which prevented correct MTU negotiation; MTU was at 1280 instead of 1500 because I’m connected through a tunnel). If fetch had used IPv4 by default like wget does, I would never have seen this.
Of course, if wget was compiled with ipv6
I want to make a FreeBSD machine act as the IPv6 router for my network and use the aiccu configured tunnel but I can’t find any instructions on this. rtadvd doesn’t seem to do anything – using gif, (assuming everything else is ok).
[...] #ipv6 und #wget: http://www.rfc1149.net/blog/2007/10/31/using-ipv6-by-default-with-wget/ [...]