For most users who are using the newer versions of the AirPort Extreme, the only drawback to configuring the AirPort Extreme in bridge mode is the the loss of the Guest Network feature. There are some other things that you cannot do as well, but if you are not missing them now, you weren't using the features or functions before, so letting the Actiontec handle DHCP and NAT should be just fine.
If you do want the AirPort Extreme to provide the DHCP and NAT services, you'll need to configure the Actiontec as a simple bridge only modem and setup the PPPoE service on the AirPort Extreme to avoid the inevitable Double NAT error messages.
Message was edited by: Bob Timmons
Bob, a few questions:
1. Can you tell us some of the things we miss besides the Guest Network if we bridge the ActionTech DSL modem?
2. On my ActionTec I can let it do the PPPoE and turn off the DHCP/NAT and turn both on in Time Capsule. Would you call that "semi-bridge" mode? Is this advisable? Is there any reason why it would be better to let Time Cap do the DHCP stuff and not the Action Tech? Maybe better speed or performance? What is the better router... Time Cap or the ActionTec DSL.