FAQ : DNS : The Internet is slow now I've enabled IPv6 (Broken DNS servers that don't support AAAA records)

The Internet is slow now I've enabled IPv6 (Broken DNS servers that don't support AAAA records)

Some users disable IPv6 functionality in their operating system to "increase their connection speed" behind faulty routers or ISP connections. This should not be an issue for most users but does occur quite often.

The real issue here is that when a host becomes IPv6 enabled it will start doing queries for 'AAAA' DNS records. As some routers (actually a NAT box) or the upstream DNS have faulty DNS implementations, instead of answering the questing for an 'AAAA' DNS record, they simply ignore the question, not answering at all. This causes the computer to wait for the timeout, after which it will try to ask the question again, but now for an 'A' DNS Record, which will result in a working answer from the DNS server.

The real solution is to fix the DNS server which is causing these problems.

In general ISP DNS servers should work fine, you thus have to configure your ISPs DNS servers directly onto your computer. One can also try using OpenDNS as an alternative DNS server.

To check if your current DNS server works correctly use one of the following sections.

Windows

Run , run 'nslookup' by selecting 'Start' and then 'Run', typing in 'nslookup' and selecting 'OK'. Then in the newly popped-up window, type:

set q=aaaa
www.sixxs.net

The latter should almost immediately, or at least quickly, return and give output with at least the IPv6 address for www.sixxs.net. If it does not, then the server shown at the top is not answering AAAA queries. You can exit 'nslookup' by closing the window, by typing 'quit' or by pressing ctrl+c.

Unices

On Linux, Free/Open/NetBSD, Solaris, AIX, MacOSX etc one can use: 'dig www.sixxs.net aaaa'. This should almost directly return an answer, it will show the query time at the bottom. If it does not, then your DNS server does not answer queries for AAAA records.