Teredo is a method of tunneling IPv6 packets over IPv4 in such a way that allows the packets to travel through NAT. This can be used by peer to peer applications to allow two people behind seperate NAT's to talk to each other directly thus making the peer to peer networks more efficient.

Under Linux/FreeBSD you need to have IPv6 in your kernel, and need to install/run http://www.simphalempin.com/dev/miredo/ in client mode.

Under Windows you can use the Teredo client that comes with Windows XP SP2 and above, or prior versions with the Advanced Networking Pack. To enable this you need to run at the cmd prompt:

 ipv6 setup
 netsh interface ipv6 set teredo client

Windows can tell you whats going on by:

 netsh interface ipv6 show teredo

now you should be able to use VoIP and P2P applications that support IPv6 as if you had a real world IP address.

Teredo won't work if:

• You have a realworld IPv6 address from somewhere else.

• You have a "symmetric NAT" (check the list at the bottom of this page, and please update it!) the only solution here is to find some other way to get an IPv6 address (maybe 6to4 on your NAT device) or replace your NAT device. Sorry.

  • Linux 2.4 and above use symmetric NAT, if this is your problem, try setting up 6to4 on your Linux box instead of using Teredo.
• Theres a firewall between you and the teredo server.
• You're on a Windows domain (in that case use netsh interface ipv6 set teredo enterpriseclient instead)

Various types of NATs that do and don't work:

• Symmetric NAT (Doesn't work with teredo):

  • Linux

• Cone NAT

  • monowall (FreeBSD kernel)

CategoryNetworking