It depends on what you’re trying to achieve. In that diagram, it appears the purpose of the second router is to add more ports to the FIOS router and provide wireless N. In that case, do NOT use the WAN port of the N WiFI router, but instead connect them LAN to LAN.
Also, the N WiFi router should be using the SAME network as the FIOS, but have a unique static IP that’s otherwise not in use and not part of the FIOS router’s DHCP pool (so if the FIOS is 192.168.1.1, perhaps make the N WiFi 192.168.1.2). Finally, disable the DHCP server on the N WiFi router.
At this point the N WiFi will be nothing more than a wireless switch. Everything will use the same network, same DHCP server, same firewall, all coming from the FIOS router.
Thank you for quick reply!
Looks like I got answer for two mine topics:
WiFi distribution and two routers in one network.(I opened second thread in Two Routers in one network )
I will try to do all what you suggest me.
I promise update this topic with results.