MTS Using own router
I think i have the answer for you. I have the MTS ONT going throught a cisco switch then to my router on its own vlan. It took some heavy troubleshooting but here is what i did. The port on the switch which is connected to the modem needs to be a trunk port. I posted my config of my 2 ports:
description Connection to Mikrotik Router
switchport access vlan 15
description Connection to MTS Fion Modem
switchport trunk encapsulation dot1q
switchport trunk native vlan 15
switchport trunk allowed vlan 15
switchport mode trunk
This allowed me to go through my switch and router grabbed the same ip address as before.
Hope this helps.