Double NAT

Unless the ISP router supports a modem only mode, then there is no way to eliminate Double NAT.

I'm not clear on whether the Fios router is providing other services to the network.

It might be possible to configure the Fios router to act as a simple modem. The questions here would be:

1) Is it possible?

2) Will Fios tell you how to do it?

3) Will Fios support this type of configuration?

Rather than jump through these hoops, it would be much simpler to ask Verizon to swap the router for a simple bridge mode modem. That would eliminate the Double NAT condition, the AirPort would speed up a bit and the whole network would be more stable.

Otherwise, you will have to live with Double NAT on the network. Apple devices don't like this error, so whenever you update firmware or make an operating system update, the AirPort will likely revert to Bridge Mode and the Guest Network will disappear. So, you'll need to keep an eye on things.

This link helped me.

http://www.podfeet.com/blog/tutorials-5/how-to-configure-verizon-fios-router-to- give-network-control-to-airport-extreme/

In the end, you will still get the Double NAT warning but can choose ignore from the dropdown menu.

The important thing is that I can now access my system (specifically slingbox) from the outside.

Expanding on the thread. Ignoring the Double NAT error helped in getting internet and the aiport set up. So far, all devices can hook up to the internet via the airport. However, devices connected directly to the airport using an ethernet cable cannot connect to the internet. Is this a Double NAT side-effect? If so, what are other side effects of this "error"?

Double NAT behavior on a network is unpredictable.

The NAT error can produce any number of issues including connection problems between devices, slow Internet browsing, some websites will appear while others do not, online gaming issues, and the list goes on.

Ignoring the error is kind of like putting a piece of tape over the "Check Engine" light in your car to make problems go away. Sometimes you can get away with it, but it is not recommended.