Maxis Business fiber will having issue to setup on other router if the user want to use their phone (free line). they cannot attach to the TM modem as per this equipment is not own by maxis. If you want to use the phone line from maxis you must use their router MA131. Problem come if you want to do port forwarding when you have different firewall router which will need. what we do is to do double port forwarding.
below is the example of the port forwarding in maxis router.
as you can see the ip 192.168.2.3 actually is the firewall router behind this maxis router.
below is the firewall router. the wan ip for this router are configure as static ip receive from the maxis router. which is 192.168.2.3
what you to do is double open the port for both router.