Multi-NIC and Multi-ISP configuration (aggregation)

[Phyo W. Soe]

Hi all,

I have a question about network link aggregation. I know similar 
questions have been asked by others in the past but I haven't found any 
solution after many days of searching on the web.

Here is what I have - An Ubuntu 7.10 server to be used as a router that 
have 3 NICs. There are 2 ADSL connections (each has 3Mbps speed) coming 
from 2 ADSL modems which I want to connect to the 2 NICs on the Ubuntu 
server. (The ADSL connections are from 2 different ISPs)
The 3rd NIC will be connected to a switch which users on the LAN will 
connect to. I want to combine those 2 ADSL connections together to 
achieve higher bandwidth (hopefully 6Mbps). So, the users on the LAN 
will connect to a switch which connects to the 3rd NIC of server. All 
incoming/outgoing traffic on the 3rd NIC has to be distributed evenly on 
the other 2 NICs.

At first, I thought bonding is the solution. I later realized that, to 
create a bonding interface, one has to enter the IP address and gateway 
for the bonded interface. In my case, there are 2 gateways (from 2 ISPs) 
and 2 different IP addresses from each of the ISP and I don't think 
bonding will work.

Is there any other way of doing link aggregation? (I saw some tutorials 
on bonding PPPoE using internal ADSL modems but I don't have any 
internal modems)

Thank you so much.

Phyo