woohoo, I can finally ping the outside world from my laptop! I've disabled everything except the ath0 and urtwn0 and changed the pf nat rule to the suggested
Code:
match out on $tether_nic from !($tether_nic) nat_to ($tether_nic)
and a reboot.
Now, with a working base, I can feel much more confident that I can work my way up to what I want from here.
With regards to the single ip address for all interfaces, what would be the best way to achieve this? Before I even learned of bridges and trunks, I was going to implement it in pf, but it seems like it should be lower level than that.
Also, jggimi, when you switch to urtwn, do you manually change the dns servers in dhcpd.conf? Doesn't matter too much at the minute as I'm planning to implement a dns caching server and learning all about dns once I've got my main setup correct
Thanks very much for all your help.