How to configure 2 subnets on same LAN talk to each other

Hello All,

I need your help and advice with my home network please. Thank you for viewing this post and your help in advance.

Scenario

I changed my ISP to SPARK and received a brand new SPARK Smart Modem

The previous IPS modem was the useless NetComm NF18ACV which total control belong to the ISP customer service which has very weak signal on both 5G & 2.4G so I bought the Asus AiMesh RT-AC68U 2 Pack hoping it would improve speed and coverage.

Like the previous ISP, I connect the RT-AC68U to SPARK Mode and found:

SPARK Smart Modem

LAN IP Addrs / Gateway: 192.168.1.254

IP Addrs Pool: 192.168.1.64 ~ 253

Asus RT-AC68U - Setup under Wireless Router mode / Aimesh Router mode (default)

WAN IP 192.168.1.65

LAN IP Addrs / Gateway: 192.168.2.1

IP Addrs Pool: 192.168.2.2 ~ 254

Devices connected to ASUS are my NAS, Media Player and home computers.

Problems:

If I connected to the internet via the Asus router, I can access all mentioned above fine but if I connect via SPARK, I can't access the Asus network.

Would you be able to give me instruction (for dummies) to configure the two subnets to communicate please.

Please ask if you need more infos in order to find a solution.

Thanks a lot