Help DS718+ LAN#2 cannot access internet on LAN#1

[kossy]

Hi, I have a Synology DS718+ with 2 LAN interfaces.

• LAN#1 (192.168.1.12) is my local LAN (192.168.1.xxx).
  • It is attached to the main router (192.168.1.1) with access to Internet.
• LAN#2 (192.168.2.12) is my camera subnet (192.168.2.xxx).
  • The DHCP server is on the DS718+.
  • A Zyxel GS1920-HP8 is attached to port LAN#2.
  • POE cameras are attached to the Zyxel router.
• Connectivity:
  • Surveillance Station on Synology DS718+ can monitor the cameras.
  • Cameras on the subnet #2 are unable to access the internet, which was intended.
  • When accessing the Zyxel router (using Firefox in a Synology docker instance), I can ping
    • LAN#2 interface 192.168.2.12
    • LAN#1 interface 192.168.1.12
    • but I cannot ping the main router 192.168.1.1.

The issue comes when I need to access the subnet for first configuration of an updated camera.
I cannot access the network directly and the new camera cannot access the internet either.
I am not sure how to enable internet access to the Camera subnet, for the time of the configuration.
I do not recall how I managed to isolate the 2 subnets at the first place.

Any help would be very appreciated !
Thanks!