Apr 26, 2013

Disable Windows 7 Teredo

Have you ever found your router with several entries in its NAT table labeled as Teredo? Windows is so awesome that it tries to create them using UPnP and will create another one if the first one didn't respond. Since my router has two interfaces and the working one is the second, Windows tries to use the default (the first one) and since it isn't configured and won't respond, it can make my NAT table quite lenghty over time.

Whats Teredo?

According to Wikipedia, Teredo is a transition technology that gives full IPv6 connectivity for IPv6-capable hosts which are on the IPv4 Internet but which have no direct native connection to an IPv6 network. So if you don't plan to use IPv6, you can disable Teredo without problems.

How to avoid this behaviour?

Its quite easy, disable or unconfigure Teredo. IPv6 is needed for Windows Homegroups, so if your using them you can just redirect Teredo to localhost to avoid unnecessary garbage in your router's NAT table.

Open a command prompt (cmd) and use the following to redirect Teredo:
C:\>netsh
netsh>interface
netsh interface>teredo
netsh interface teredo>set state type=client
servername=0:0:0:0:0:0:0:1

If you want to disable it, just type:
netsh interface teredo>set state disabled

Also you can check the current state with:
netsh interface teredo>show state

Teredo Parameters
---------------------------------------------
Type                    : client
Server Name             : 0:0:0:0:0:0:0:1
Client Refresh Interval : 30 seconds
Client Port             : unspecified
State                   : offline
Error                   : failed to resolve server name