Nice guide there. If you're using your own router e.g WRT54GL, you can follow this guide.
If you're using back DIR-615 for the PPPoE, you need to set LAN Port 1, VLAN ID=500 and PVID=N/A. Then you can connect back your DIR-615 to the LAN Port 1 of the BTU without changing any configuration on the DIR-615.
Rexio....Thank U...appreciate it so much....
Silencer, this is what you need to do.
Connect your laptop/pc to Port 4 of your ZTE BTU 931
Manually set your laptop/pc I to 192.168.1.2 subnect mask 255.255.255.0, you may leave the gateway blank.
After that login to your BTU, via 192.168.1.1 and type in username and password = admin
After that, follow this screenshot below.
Disclaimer, I am not liable for any damages/down time caused to anyone. Do it at your own risk.
Port 1 (Connects to your router's WAN port)
Click on Advanced Setup > Vlan Trunk Setting
Then follow this screenshot.

Click Save/Apply
After this, click on the LAN Interface Select pull down menu on top and select LAN2
Tick vlan Trunk Enable and configure as per screenshot below
Port 2 (Connects to your IPTV)

Click Save/Apply.
Reboot your ZTE BTU and IPTV and Router.
Sohlican...really appreciate th eguide..Thank U..