I understand the set-up on the external router side of things and that's all working as expected with the router connected to LAN1 on the ZyXel.
However, I want to hook up my Raspberry Pi or another PC to either LAN2 or LAN3 (or ZyXel wireless) in order to grab DSLstats from the modem. The DHCP server on the ZyXel will (should) still be running for anything that connects to LAN2, LAN3 or Wireless. I've deliberately set the IP address of the modem to 192.168.2.1 and altered the DHCP server range accordingly.
While I can easily set-up a static IP on one of those devices to connect to the modem, and that is currently working, I'm struggling to understand why the ZyXel DHCP server isn't allocating an address automatically when it was doing it fine during the off-line set-up (while in Bridge mode, not router mode)
When I set-up the modem, the first thing I did was reset it to factory defaults, and then configured as per Kitz guide, and changed the local IP address and DHCP range. This morning before swapping out the HG612, I turned it on, connected a cable from my PC to LAN2, and connected to the Web GUI so that I could put the 15 firmware on it. I had no issues with that, the ZyXel DHCP server issued an IP address to my PC no problem at all. The ZyXel was still in bridge mode, and I know connecting to LAN1 wouldn't work as that's part of the Bridge group. The firmware updated fine, checked I could login after the update, and all was still well.
So I'm struggling to understand why the DHCP server would now not be working.