is there a way to turn off the NAT of the FIOS router??
That is a question for the FIOS support folks. But, you would want to turn off both DHCP and NAT on the FIOS router, which would place it in modem mode. Then, the TC could be configured in router mode to supply the DHCP and NAT service and all would be well.
In other words....one device needs to be in Bridge Mode. That can either be the FIOS device and the TC acts as a router.....or....the FIOS acts as the router and the TC is in Bridge Mode.
The likely problem with trying to configure the FIOS router in Bridge Mode....even if it can be done....is that I doubt that you would receive support from FIOS in this type of configuration...and...you will likely lose some of the FIOS features that you have now.
yes understood..i would think this is all a common problem because today most people have cable or FIOS for there TV/internet and they supply you with a combo router/modem and even the TC instructions tell you to hook up the eternet cable from your router to the TC WAN port..and then the default for the TC is Bridge mode with no Guest network..and after selling the TC having a Guest feature...well they must get calls asking why/where is it..
OK just to put this to bed, I called Apple support. They pretty much verified everything we talked about..in bridge mode no Guest network..you have to choose the option for NAT ..He said they tell people to turn off the FIOS wireless...and have everything join the TC network. (printers, apple tv, wii). I would not turn off the FIOS wireless because your TV DVR boxes talk to each other via the network and they require no set up to join the fIOS router..they however have no way of changing the network to the TC so they will have issue and also if you need FIOS support they will not be able to work on the boxes..so for now its a double NAT setting and have the option of enabling the Guest network when I want.