As a user of TomatoUSB powered router
It
SHOULD work when UPNP is enabled as in testing/troubleshooting the remote play handshaking procedure... No connections were being blocked by the firewall/router with and without the PS4 being DMZ'd, I even tried static IP address which didn't solve the issue...
Finally enabled uPNP (I don't like it as it can produce funny results sometimes when I DMZ a console and the console will set some uPNP rules which actually causes ports to be blocked instead of allowed)
Researching this issue, I've noticed most users that are having issues have Apple AirPort Extreme routers...
https://discussions.apple.com/thread/5218964
I wonder why they wouldn't have uPNP support... /sarcasm (Because they like using their less popular bullshit bonjour protocol)