Backhauls and Vlans

We have an install where we are installing a backhaul to a business customer and we want to know how can we tag the vlan so that the customer would be on valn 100 which is out public ips.

You’ll need to tag before it enters the BH as the BH’s do not do VLAN tagging.

yea it will pass threw with vlan 100 but do i need a layer 2 switch so that there computer will see the vlan 100

Yes, just put a VLAN switch in that tags the customer port with your VLAN ID and you should be good.