DSL Network

We presently have a LAN with 253 Public IP Addresses because many of the people need to get to a VPN. We have grown and need to have more people get internet access. So the question is, I think we need to get another DSL line to run over the same switches and backbone. We don’t need anymore Public addresses. NAT is fine for the other people. What do I need to get or know to allow 2 DSL’s to be available on my LAN. Presently the DSL goes into a flowpoint router. We have no firewall.