@Clive_A Till this point I understood that if we use the IPTV option, we can split the 2 VLANS , one is Internet and another is VOIP. 

I have one ISP which sends INTERNET in VLAN 100 and VOIP in VLAN 200. I put the Fiber ONT in bridge mode and both the VLANs are tagged to the single LAN port of Fiber ONT. 

Say, I use IPTV and use the custom mode on WAN 1 and specify Internet as LAN 2 , 3 and 4 and LAN 5 is for IP-Phone. For the WAN 1, I configured PPPoE and mentioned the VLAN number 100. How would I get a DHCP address on LAN 5 since my VOIP runs through DHCP mechanism. I am unable to get this point. The DHCP option for VLAN 200 is not possible in Fiber ONT as it is in Bridge mode. There is no place in ER605 where I can mention that LAN 5 VOIP address needs to be obtained via DHCP from the ISP. 

So how to make this set up working ?

  @AMOHAN 

AMOHAN wrote

  @Clive_A Till this point I understood that if we use the IPTV option, we can split the 2 VLANS , one is Internet and another is VOIP. 

 

I have one ISP which sends INTERNET in VLAN 100 and VOIP in VLAN 200. I put the Fiber ONT in bridge mode and both the VLANs are tagged to the single LAN port of Fiber ONT. 

 

Say, I use IPTV and use the custom mode on WAN 1 and specify Internet as LAN 2 , 3 and 4 and LAN 5 is for IP-Phone. For the WAN 1, I configured PPPoE and mentioned the VLAN number 100. How would I get a DHCP address on LAN 5 since my VOIP runs through DHCP mechanism. I am unable to get this point. The DHCP option for VLAN 200 is not possible in Fiber ONT as it is in Bridge mode. There is no place in ER605 where I can mention that LAN 5 VOIP address needs to be obtained via DHCP from the ISP. 

 

So how to make this set up working ?

ISP require the PPPoE and VLAN ID, you input them in WAN settings.

Then go to the IPTV setting tab and input the VLAN for different purposes. 

IP are DHCP defined from the router. Not from your ISP. The router will NAT and distribute data for different purposes.