ipv6 route is favored ?

[sgoudelis]

I have managed to make everything work nicely with dd-wrt and linux debian routers. I have noticed something however. When browsing websites that also resolve to ipv6 address, the ipv6 route is favored and used. Is it possible to always use the ipv4 route if both are available and only go to ipv6 when an ipv6 address is provided alone ?

[kriteknetworks]

Just curious, but why would you want this? I don't understand your desire to avoid ipv6 when an ipv4 destination also exists.

[cholzhauer]

I'm with kriteknetworks. 

But, yes, you should be able to change this.  What OS are you running? Debian?

[sgoudelis]

Well consider this example: In ubuntu, when downloading updates with aptitude, if the repo host also resolves to an ipv6 addr, that route is used to download. I live in greece and the ping time to the ipv6 tunnel startpoint is about 100ms. This make the downloads very slow. Same scenario applies in browsers and elsewhere I assume.

But, yes, you should be able to change this.  What OS are you running? Debian?

Ubuntu, debian, mac os, windows etc. Please provide one example and I ll replicate where needed.

Thanks guys..

[cholzhauer]

From http://www.dd-wrt.com/wiki/index.php/IPv6

6to4 IPv6 as default protocol

As per RFC3484 §2.1 default policy table, having a 6to4 enabled LAN (using a 6to4 anycast tunel on a DD-WRT enabled box, say) will 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 IPv4 default on IPv6 enabled Windows boxes using 6to4 prefixes.

1. Start -> Run -> "cmd" -> "netsh" -> "interface" -> "ipv6"

2. To enable IPv6 preference 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 Voilà ;-)

Notes: ::1/128 == localhost, ::/0 == default, 2002::/16 == 6to4, ::/96 + ::ffff::0/96 == IPv4 compatibility, 2001::/32 == Teredo, 2000::/3 would be All IPv6 Global Unicast address space

[sgoudelis]

Yeah, I shouldn't have said windows. I have no idea what is happening above. Thanks anyway. If someone finds something please post here...

[cholzhauer]

Look at reply#2 here

http://www.tunnelbroker.net/forums/index.php?topic=747.0