Is it possible to merge multiple internet connections?

I've tested dual-WAN on two ADSL2-connections and found out that the Linux solution was quite tricky to setup and it wasn't very reliable. I am now running PFSense on a old PC with 3 network cards. It was very simple to install, just boot the live-CD and connect LAN, WAN and OPT (second WAN) network cables to NICs when the installer asks. Then configuring the actual dual-WAN with failover was very simple, a guide can be found here:

http://doc.pfsense.org/index.php/Multi_WAN_/_Load_Balancing

If you don't want to use a dedicated PC for routing, I think it is possible to install PFSense on a VMWare (or similar) on your Windows XP and allow it to do the routing for you. This would ofcourse add some CPU overhead and use couple hundred megs of RAM.

windows does support load balancing of WAN connections.

I haven't tried this so do at your own risk.

You can try opening up the registry under: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBT\Parameters

And setting/adding these DWORD values RandomAdapter = 1 SingleResponse = 1

Reboot your computer.

See: http://www.vietcyber.com/forums/showthread.php?t=127328 or http://www.techsupportforum.com/networking-forum/networking-support/101350-manage-two-internet-connections-same-pc.html

the easiest way is to use some scripting to check connectivity to each gateway, and based on that, switch to the secondary line when the main line is down

see this and you can start from something like this

ping -n 1 gateway & if %ERRORLEVEL% not zero then (commands from the tutorial in the previous answer for changing default gw)

and this batch should be run from task scheduler as often as you want

Linksys has a router which can support multiple internet connections and failover between them automatically. It's not that expensive, less than $200 I think. The rv042 is what you are looking for. It looks like Amazon has it for ~$150 US.