Win7 seems to prefer IPv4 native to IPv6/6to4 - which is not what the policy table says - which is right?
I have a Win7 machine. It has an IPv4 address, and an IPv6 address via 6to4 (from upstream - the PC is not the 6to4 site router). I believe that IPv6 should preferred to www.ietf.org, which has both IPv4 and IPv6 records in the DNS. It is not, however. Both "ping www.ietf.org" and using a web-browser to that same name use IPv4. I can see the DNS queries go out and an A and AAAA record returned. My prefix policy table shows IPv6 should be preferred. Unless I don't know how to read it, 6to4 is clearly precedence 40, and native IPv4 is precedence 10. Be clear I am not using IPv6/Teredo - I expect IPv4 to be preferred to that. But I expect 6to4 to be preferred to IPv4.What is going on?My prefix table:C:\Windows\system32>netsh int ipv6 sho prefixQuerying active state... Precedence Label Prefix---------- ----- -------------------------------- 50 0 ::1/128 40 1 ::/0 30 2 2002::/16 20 3 ::/96 10 4 ::ffff:0:0/96 5 5 2001::/32
November 18th, 2009 1:49am

Precedence Label Prefix------------- ------ -------------------------------- 500 ::1/128 = localhost 401::/0= default (IPv6 native) 30 22002::/16=6to4 (IPv6)20 3::/96 = IPv4 compatibility 10 4::ffff:0:0/96 =IPv4 compatibility 5 52001::/32= Teredo (IPv6)http://www.dd-wrt.com/wiki/index.php/IPv6_%28tutorial%29#6to4_IPv6_as_default_protocolQuote:6to4 IPv6 as default protocolAs per RFC3484 2.1 default policy table, having a 6to4 enabled LANwill mean that 6to4 IPv6 will only be used to communicate to a server if the server is having a 6to4 adress too (ie: 2002: prefix on its address) or if there is no IPv4 address assigned to the server name (ie: no A but an AAAA). In short the following makes IPv6(6to4) default on IPv6 enabled Windows boxes:1. Start -> Run -> "cmd" -> "netsh" -> "interface" -> "ipv6" 2. Toset IPv6 (6to4)as thedefault protocol on Microsoft Windows... set prefix::1/128 50 0 set prefix::/0 40 1 set prefix 2002::/16 30 1 set prefix::/96 20 3 set prefix::ffff:0/96 10 4 set prefix 2001::/32 5 5 Only the 2002::/16 line (6to4 prefix policy) is changed. 3. To make things goes back to original mode (IPv4 preference)... set prefix::1/128 50 0 set prefix::/0 40 1 set prefix 2002::/16 30 2 set prefix::/96 20 3 set prefix::ffff:0/96 10 4 set prefix 2001::/32 5 5 And Voil;-) Shorter method also available here: http://oldwiki.openwrt.org/IPv6_howto.html#head-a7f78c2c72f1b6d3899b5b8587e5067a77170896
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November 21st, 2009 7:26am

Awesome help for Windows 7, but can you tell me how to do this for Vista please? I followed the steps and it worked for my Windows 7 machines, but when I did it on Vista it didn't work at all :(
July 20th, 2011 4:19am

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