How can I remedy a multiple AirPort network where each base station tends to end up isolated from the rest?

Question

I live in a wide house, so I have an Airport extreme, an Airport express and a TimeCapsule setting up a free roaming network. I used to have the Airport Express working as a master central router for the rest of the network.
Airplay was a little buggy and wifi gaming is not the best option out in the market.

But now I changed my ISP, and it provided me (free of charge) with a ZTE ZXDSL 9311WII routed modem, with 4 ethernet ports, so I decided to boost the performance of my network. Bought over 300ft of LAN cable, a bunch of cable connectors, crimping tools and even wall connectors...
So I wired every AirPort directly to the ZTE, and now I have all airports in bridge mode.

The problem that emerged is that a computer connected to one airport can not see anymore the computer in another airport. This happens if the computer is connected via wifi also, he can only see the ones connected to the same airport. Also, airport admin utility lost the capability of seeing all the airports connected and turned on - and now can only see only the one that the computer is directly connected to.

How do I solve this visibility issue?

I am SURE ZTE is not blocking connections because if I plug in computers directly to ZTE, they can see each other just as they should.
I already went trough all airport possible configurations, googled for the whole day, and found nothing about this configuration being possible or not.

Answer 1

Apple's free roaming network with their AirPort and Time Capsule routers works great... as long as you're using one of their devices as the master DHCP server and link to the DSL modem.

Once you switch from "Extend a network" into "Bridge" mode, you lose all ability to free roam.

At both my parent's home and my office I have the DLS modem (the ZTE ZXDSL in your case), a switch (can be built into the modem) and various AirPorts and/or Time Capsules.

Turn off all the Apple routers except one and start with that one. Configure it to be the main link and the DHCP server. Make sure it talks to the internet and does everything you want.

Next, configure the next Apple wireless router. Sometimes you need to reset them back to baseline configuration and then begin from there. As it comes up, use the wizard to select "Extend a network" and follow the prompts to input the info for your network. Make sure everything works to connect to the internet with both Apple routers.

Repeat the procedure with the third.

Having the AirPorts hard-wired together provides the best infrastructure between the access points.

Enjoy your free roaming.