Currently Being ModeratedMar 17, 2013 12:21 PM (in response to Hans Kjellberg)
How is the modem setup? Are you running it bridged or as full router or do you have a special mode like ipoa?
If the modem is working as router, bridge the TC in isolation from the network. Just select bridge in the airport utility.
That is v5 utility .. in v6 it is under network tab. Same option..
If the modem is bridged then you need to use the pppoe wan setup?
Did you try that?