Question : Internet & Network Integration - Elegant Solution Needed!

Here's the setup:
 * One ADSL 2048/512 connection (fixed IP) connected to a USR 9106 Wireless Gateway/Modem/Router
 * One cable 512/128 connection connected to a Micronet SP888 Cable Router
 * Two NIC's in one main computer running XP Pro.
 * Another 3-4 computers are waiting for the answer to this question to be plugged into correct gadgets.

Aim: To share resources among the network and provide internet access to everything connected. (Can be an either/or solution with the cable and the ADSL, but the main machine has to access both - even if not simultaneously.)

Note: Please do not tell me to get a dual WAN router, as I can not locate them around where I live. Can get pretty much everything else, though. The issue is I'd like both connections to be available, preferably at the same time.

First off, let me state for the record that everything works, and they are at default settings. Now, a couple of questions:
 1. Although both NIC's work together, I can choose via the XP control panel which NIC to activate and my WAN IP changes on the fly. What is actually happening, is one NIC receiving a redundant stream? Although only the active NIC handles the Internet, the other router's LAN activity lights are flashing as well, indicating that it's feeding the system some info.

 2. What actually happens if I "bridge" these two connections from the Network Panel? I have tried this and could not notice any change on the WAN side - speedwise or ping times.

 3. Does XP Pro maintain separate registry entries for each NIC? I have "optimized" the NIC going to the ADSL router with values for a PPPoE connection. Do these values also apply to the NIC handling the cable connection? (Each type of connection requires slighly different values, it seems)

 4. What would be an ideal setup/values for a connection with the least latency? This is topmost priority as my son and I play online games, specifically StarWars Galaxies where ping times are cruical.

 5. Right now, the USR sits at 192.168.1.1 - assigns me 192.168.1.3 via DHCP on one NIC, the Micronet at 192.168.1.111, giving me 192.168.1.4 on the other NIC. All 255.255.255.0. Technically works OK. Both routers respond to their setup pages, but only if turn off the other NIC. I can telnet to the USR unit and issue complicated unix commands. (Could have been a different segment, but I'm trying to discover things here) Is this a technically feasible setup? Can there be two DHCP servers/gateways in one IP segment ? Seems the XP has no way to manually assign priority on one NIC. Am I missing anything?

 6. If I connected machines on both routers in this setup, will they see eachother? But this is really not the way I'd like to solve this. I would ideally like all machines to be able to choose one gateway or the other (cable or ADSL, so to speak) on the fly, still maintain DHCP / router capabilities, AND interconnectivity.

 7. I have been reading about gateway/router computers running Linux for a more elegant solution. Can this venture provide me with redundant and/or load-sharing capabilities? Will it really be a more elegant and useful way to go? (maybe a proxy, as well?) I can scrape up another machine for this purpose, but being a novice, most info just flies over my head. Any useful pointers here?
I guess what I'm really looking for is "A guide for the network-challenged to integrate dual WAN capability and still maintain file-sharing among all machines on a network using a Linux box "..

I'm thanking you all in advance, and really looking forward to hearing your expert opinions on this. Cheers..

Answer : Internet & Network Integration - Elegant Solution Needed!

First off, there should only be one DHCP server per layer 2 network.  If you have more than one, there is no way to prioritize them.

2nd, you should reserve DHCP for the devices inside your network.  You should not use DHCP to configure network devices that you count on to do networking functions.

Here's what I would do.  You need to route - or make routing decisions based on network metrics.  Unfortunately, you know nothing about what is closer / faster on either network provider's service.  They are not going to provide you with routing tables... so you have to guess as you go and manually configure them.

Split routing across the two connections is going to be problemmatic.  You can't open up a web page through one service provider and the switch your session midstream to the other.  The site will see you as a new visitor.

I would disable DHCP on the two connection devices.  Use a small 4-port switch to connect the ethernets from the DSL modem and Cable modem.

Now, get a DSL/Cable Router - like a Linksys 4 port firewall/router.  Turn off the firewall and NAT features.  Set it up as a "router".  Plug its WAN connection into the 4-port switch, making a small network of 3 devices - the DSL's ethernet, the cable's ethernet and the Linksys's WAN.  Plug in the rest of your network behind the linksys on one of its 4 LAN ports.

Assign your new Linksys with an "outside" address of 192.168.1.200 (or anything in 192.168.1.x Except x=0, 255, 1, 111).  Set it up with an Inside address of 192.168.2.1.  Set it up to provide DHCP addresses to computers in your network as 192.168.2.x.

Next, define static routes in the Linksys router to divvy up your traffic.

Start with the "Default route" 0.0.0.0 0.0.0.0 to go to your preferred (higher bandwidth) DSL connection 192.168.1.1.  You can set up the other device as your "backup" connection by setting the same default route to 192.168.1.111, but with a higher hop-count.

Set routes for certain other networks manually by giving their network address and mask and sending the traffic to a particular outside network (either 192.168.1.1 or 192.168.1.111).

The Linksys has a limited number of static routes, so use them carefully.  You'll never get a full balance between the two connections.

It's not elegant, but it will work.... and for an out of pocket expense of less than $100, it should work pretty well.