Airport IPv6 Router Advertisments? I have a working HE.net IPv6 tunnel configured on my Apple Airport Express but the rest of the machines on my LAN aren't picking it up automatically.  Connected machines work fine if I configure IPv6 on them manually.

Sniffing the network appears to show that there aren't any RA packets being sent.

I seem to recall reading that the Airport will only send RAs if it has a private (RFC 1918) address on its ethernet port.  Mine doesn't - I have public IPv4 addresses.

Can anyone confirm this, or offer a work around?
Make sure your Airport Express is updated to the latest firmware. Up until recently the Airport Express would get an IPv6 address for itself but would not issue them via DCHP which is why you needed to do it manually. This may be what's happening for you. The Airport Extreme only gained DHCP support for this at the last firmware update so I'd assume the Express did too but I don't have a newer AE to know for use and the older model doesn't support IPv6 at all.