Combine Multiple VLANS into one single broadcast domain

Hi,

I have a scenario where a wholesale provider is handling over customer connections in VLANs.

I am running the connections through a Juniper switch in order to use the DHCP Option 82 and IPV6 equivalent circuit tagging to ID each customer.

How in a Juniper switch would I combine all of these VLANs together into one broadcast domain? In effect each VLAN acts like a cable into a simple switch.