How to configure 6to4 in MacOS X

Later versions of MacOS X support 6to4. Problem is, before Panther there wasn't a GUI interface to it. Even in Panther, the GUI for 6to4 is sort of difficult to find. Since as co-author of the spec I naturally think 6to4 should be widely used, I thought I'd take the time to describe how to do this.

Panther (and presumably later).

1. Pull down (apple) / Location / Network Preferences (or run System Preferences and click on Network)
2. At the top of the Network window, select some network location from the Location: menu
3. now at the Show: menu (underneath Location:), select "Network Port Configurations"
4. If you don't see 6to4 listed, click "New..." (if you do see it listed, check the check box)
5. In the popup window, under "Port..." select "6 to 4" and give it a name, like say, "6to4"
   
6. Now 6to4 will show up as one of the check boxes under "Network Port Configurations". You can also select 6to4 from the "Show..." menu if you need to configure it.
   
7. The only reason you need to configure 6to4 is if the default relay router doesn't work and you want to assign a manual one. Change the "Configure:" menu from "Automatically" to "Manually" if you need to do that. Then it will let you type in the address of a 6to4 relay router.

This is actually fairly convenient as you can selectively enable 6to4 on a per-location basis - so I have it enabled for locations where there isn't already IPv6 access and I have it turned off for locations where IPv6 access exists, or where there's a NAT that prevents 6to4 from working.

Jaguar (perhaps earlier?)

1. Open a terminal window
2. Type sudo ipconfig start-stf

That should be all that's needed. In rare cases you might need to edit /etc/6to4.conf as root, but the default values will often be sufficient. Type man ip6config in a terminal window for more information about how to use ip6config.

The downside is that you have to do this every time you want to use 6to4 after reboot - I don't know of any way to make it happen automagically when the network is configured or when you select a location. Also, I don't know what happens if you change locations while this is running. My guess is that you need to do sudo ipconfig stop-stf, change the location, and then do sudo ipconfig start-stf again.