Double NAT problem (Fastweb NEXXT .it)

Hi there, Long time user first time poster;
I'm using a Netgear WNDR3700 v4 with OpenWrt 21.02.1 r16325-88151b8303 / LuCI openwrt-21.02 branch git-21.295.67054-13df80d.

I'm having the Double NAT problem and looking for a bit of advice; presently the above router is operating behind a fastweb nexxt - VDSL2+ modem/router/f***ing alexa (seriously WHY!?), which only has the option to partial DMZ( it blocks a whole range of ports because reasons) and you can't put it into bridge/modem mode... because presumably it would make alexa cry.

naturally for about 95% of the traffic through the network it's not a problem but when it comes to gaming we're having issues, and also I quite like my PiHole adblocking. anyone know any tips or tricks (short of buying a VDSL2+ modem).
the fastweb abomination doesn't have the option to set a local DNS, it doesn't even have the option to disable DHCP.

so I'm kinda stuck.
p.s. also UPNP doesn't work (for gaming) I can forward ports manually, but nobody likes getting error messages.

If the fastweb unit doesn't really support DMZ properly, just simply forward the specific ports you need to your OpenWrt router's WAN. You should be able to find documentation for the required ports on the game and/or console websites.

For this, I'd recommend finding sites/forums where people have specific experience with this device. You may or may not get any relevant replies here because this forum doesn't specifically focus on modems.

There's nothing that can be done about this... it's just how UPNP works (it'll open the ports on the router that is connected to the device making the UPNP calls (your gaming system), but the upstream router does not get triggered for this). If UPNP is a must have for you, the options are to but a DSL modem that operates in true bridge mode, or to connect the game system directly to the fastweb box.

Appreciate the response, it confirms what I already knew, I was just throwing it out because I figured there might have been something I was completely unaware of.

I wonder if there's a bridge protocol/function where it's possible to repeat/mirror the information from the ISP device but honestly I reckon that's probably fantasy.

The ISP supplied modem is a total joke frankly, although I understand that for 99% of customers is perfectly adequate, I'll have to try contacting them to see if it's even possible to put it into bridge/modem mode, although I have my doubts. Not to mention my lousy technical Italian...

picked up an AVM FRITZ 7360v2 off of ebay. I'm prepared to throw €27 at the problem. I'll either configure it as bridge or I'll reconfigure the other router as a WAP/switch because I'm a bit lazy that way (and the WiFi from the AVM box is garbage - from experience).

I'll post the results in the event someone else searches for this specific ISP modem

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