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sixxs.net often resolves to IPv4

Shadow Hawkins on Friday, 02 April 2010 19:27:30

Hello, I have a strange problem with reaching the sixxs.net website. Most of the time, I'm presented with the IPv4 version instead of the IPv6 site. DNS resolution works like a charm and shows both A and AAAA records, and all other sites having combined records always resolve to the IPv6 address (like kame.net, ripe.net or hostblogger.de). I'm not behind a proxy. My router seems to correctly resolve the IPv6 address, while my Mac client doesn't. As sixxs.net is the only site facing these problems, I guess it has something to do with AICCU (my tunnel is hearbeat). Anyone else experienced these problems before? Thanks, Florian

sixxs.net often resolves to IPv4

Jeroen Massar SixXS Staff

on Friday, 02 April 2010 19:49:52

I have a strange problem with reaching the sixxs.net website.

What exact URL are you trying? What is your OS, webbrower versions etc?

[..] while my Mac client doesn't.

Something on a Mac, well, OS X apparently has a 'first DNS response is the one we take' thing, which might be causing exactly the problem that you are seeing. Ask around on the Apple IPv6 lists for this though.

sixxs.net often resolves to IPv4

Shadow Hawkins SixXS PoP Administrator

on Friday, 02 April 2010 20:05:24

OS X 10.6? On a quick search I found random pointers towards problems introduced by a strange mDNSresponder-behaviour. http://openradar.appspot.com/7333104 http://osdir.com/ml/ipv6-dev/2010-02/msg00005.html http://www.mail-archive.com/tech@lopsa.org/msg01273.html http://www.fix6.net/archives/2010/03/06/the-strange-behavior-of-apples-mdnsresponder/ Hope that helps. If you maybe find a workaround until the bug gets properly fixed, maybe let us know.

sixxs.net often resolves to IPv4

Shadow Hawkins on Monday, 05 April 2010 13:30:04

Hi Jeroen, Hi Stefan, thanks for the reply! I tested with my router (Ubuntu, lynx) and it does seem to work there, while on my OS X 10.6.3 machine with Firefox 3.6, it doesn't work reliably. Maybe it was a coincidence, but as soon as I tried on the router, the correct IPv6 has also been used on the client. I've tried various sites, and the problem *only* occurs on SiXXS. Various other sites with mixed A and AAAA records work fine. Either it has something to do with the CNAME you use (www -> CNAME -> nginx.sixxs.net), or with my way of tunneling. I doubt it's the Apple bug, but I'm no expert. One idea is that my local DNS at first only has IPv4 connectivity, resolves sixxs.net to establish the tunnel via AICCU, and afterwards doesn't bother to transport IPv6 records... just an idea, but I'll look into it and probably just flush the DNS cache after the dialup. :-) Florian

sixxs.net often resolves to IPv4

Shadow Hawkins on Tuesday, 06 April 2010 14:04:25

I've tried various sites, and the problem *only* occurs on SiXXS.

No, (rarely, fortunately) I have the same issue with other hosts. It becomes an actual problem when the hostname you're trying to resolve only has AAAA records Even if you run a local DNS server, queries are cached by mDNSResponder - restarting BIND won't solve your problem. Purging the cache makes mDNSResponder happy (sudo killall -HUP mDNSResponder; note: sometimes you have to execute that command more than one time).

sixxs.net often resolves to IPv4

Shadow Hawkins on Wednesday, 14 April 2010 19:10:39

Hi Roberto, thanks for the tip, but it doesn't work. Tried it about 10 times, nothing changed. Will investigate further and with a second host to see where the culprit lies... Florian

sixxs.net often resolves to IPv4

Shadow Hawkins on Tuesday, 06 April 2010 08:28:30

Hi, just a short update: Neither restarting my local BIND instance, nor accessing sixxs.net directly from the router do impact the reachability via IPv6, I just tested it. Florian

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