I have a DSL and a T1 circuit coming into a HP Procurve 4000m. I have a LAN of 40 comps. Half of them are on T1 and half of them on DSL. Computer A has IPs assigned to it from both networks. However how do I control or tell the computer which IP to use when it goes online? Right now it uses the xx.xx.xx.8 (DSL) vs. xx.xx.xx.68 (t1). Further more, is there way to enable the comp to utilize both the DSL & T1 simultaneously?

Running two upstream Internet providers like that through a single switch is a bit messy. Ideally, you would have a router sitting between each Internet connection and the rest of your network(s). But, since you don't - create one VLAN on the switch for each Internet connection. DSL + computers using DSL go on one vlan, T1 + computers using T1 go on the other. You might be able to get the one computer to utilize both Internet connections by connection teaming. I don't know if this would work, and I wouldn't recommend trying. If you need to load balance your network or make it fault tolerant, use routers. That is what they are designed for. If you don't need load balancing or fault tolerance, then you probably need to rethink why you want this one computer use both connections.

Dear jimminy, Thank you for your response. My DSL lines comes in through an ISP's modem, then hits MY Cisco 1721 Router, then goes to the switch. My T1 comes through an ISP's Cisco router, and then into the switch. Now the reason that I have two networks (same subnet and 128 sequential IPs split evently between the circuits) is that this is a LAN center and I need as much bandwidth as I can get. Now the reason for this thread, is that as a LAN center, I host Counter Strike servers, and that's where I ran into problems. The CS server is hosted of a T1 line, however my DSL computers would ping like they are on WAN, not on LAN. Due to the fact that tracert showed that the traffic from DSL computer traveled outside my network prior to connecting to the T1 computer (CS Server). So in turn I assigned a secondary IP to the T1 computer (CS server), but since the DSL ip is xx.xx.xx.8 and T1 IP is xx.xx.xx.68, it seems that the computer is utilizing the DSL line instead of T1. That's where my main question lies. How do I control that?

Ok, that makes sense :) Does the server need to be on both the T1 and DSL networks? If not, you could just statically assign its address and prevent it from leasing an address from either network. There are other ways to accomplish the same thing, but this is probably going to be the simplest. If the server does need to be on both networks - I'll have to think about that.

Dear Jimminy, I have 128 static IPs assigned to me. The CS server computer would either need to be on both networks or an alternative way for my DSL computers to connect directly to the T1 (CS server) computer without leaving my switch and my network. Regards, Denis

Ok. You can leave it multihomed on both networks. Set the T1 gateway address as the default gateway - by default all IP traffic will be routed through this interface. Create static route(s), using the DSL network's gateay, for communication with the DSL network. Only IP traffic to and from the DSL network will use those routes (and by extention, that interface). Hope you can make sense of that. If not, I'll try to rephrase it when I'm not so tired. Good luck :)

Dear Jim, If you could rephrase that, it would be greatly appreceated. How exactly do I tell application which interface to utilize? Regards. Denis