IPv6, 6in4 tunnel - GUI only
From DD-WRT Wiki
What is 6in4 tunnel?
6in4 is an Internet transition mechanism for migrating from Internet Protocol version 4 (IPv4) to IPv6.
6in4 uses tunneling to encapsulate IPv6 traffic over explicitly-configured IPv4 links as defined in RFC 4213 (obsoletes RFC 2893 and RFC 1933).
6to4 is not equal 6in4?
No. 6to4 is an Internet transition mechanism for migrating from IPv4 to IPv6, a system that allows IPv6 packets to be transmitted over an IPv4 network (generally the IPv4 Internet) without the need to configure explicit tunnels. Special relay servers are also in place that allow 6to4 networks to communicate with native IPv6 networks.
In another words, if you only get IPv4 from your ISP, but you want to be able to reach IPv6 sites, 6in4 is one of your solutions. It is simple and free with a just few of clicks in ddwrt GUI:)
First thig you need to do is to create your account at HE.net IPv6 Tunnel Broker
After creating an account, return back to main page to create a tunnel. Choose your nearest location.
Click on Host/Identifier: The DNS fully-qualified name of your tunnel, not the numeric Tunnel ID.
This is of the form <user>-<index>.tunnel.<tunnel-server>.<datacenter>.ipv6.he.net.
Now, setup your ddwrt and enable radvd as shown on screenshots. Pay attention on MTU (generally wanif MTU - 20).
If you prefer you can use DNSMasq, for router advertisements, instead of Radvd.
Just put this commands in Additional DNSMasq Options (Services tab of your ddwrt):
interface=br0 enable-ra dhcp-range=::1000,::FFFF,constructor:br0,ra-names,5m dhcp-option=option6:dns-server,[::ffff:d043:dede],[::ffff:d043:dcdc] ra-param=br0,10,300 quiet-ra quiet-dhcp quiet-dhcp6
About MTU you can read HERE and HERE Don't go under 1280 because it is the minimum IPv6 packet size. You also need to accept ping (icmp protocol) from HE server to. So save this command as your firewall rule:
iptables -I INPUT 2 -s 66.220.2.74 -p icmp -j ACCEPT
If your ISP provides you with dynamic IP than you need announce every change on HE. You can use DNS-O-MATIC method.
Now, if everything is ok, you should be able to ping ipv6.google from your PC (MS Win) command prompt:
ping -6 ipv6.google.com
If you have problem with your win machines read this
special thx to JAMESMTL