To have a static IP with the router in the network just reserve the IP the router is giving your device or just specify one within your DHCP scope.
Setting > Network Settings > Add DHCP Reservation
What device would you be talking about?
One thing that I think that interferes my progress of fixing the problem is- I'm used the gateway's IP to get into the router or w.e that is. I didn't use the D-Link's IP because I tried to use it but I have no idea what the password is for the D-Link server. So I believe doing all these steps such as port forwarding is a waste of time because i'm not doing it correctly ? O boy i'm sooooo confused i've completely hit a wall.
Here's how it goes one more time Globe > Gateway > D-Link > ? > Laptop/Xbox
I used the Gateway's ip not the D-Link's.
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Right now I just went back to the gigafast site and the option DMZ was available & I changed a couple of settings such as enabling the DHCP. Once I apply these settings. It will take effect on the the Gateway itself right ... how about the d-link router itself will I need to do the same process to the router aswell ?