On 29 April 2015 at 18:14, mick mbm@rlogin.net wrote:
I think I can see what you are trying to do, but I see a problem. What is your default route to the wider internet?
All you internal systems will have a default route set as 192.168.100.1. But which router does that box choose to send traffic out? You could set up your own routing table partitioning the outside world into three bloody great subnets and allocating one to each of the ADSL routers, but that is asking a lot of your little domestic setup. Alternatively, you have one default route allocated, but I don't see how that helps you since the other two routers then become redundant.
Basic load sharing (and fail-over) is do-able, typically using a round-robin approach (maybe with some weighting). So each outbound connection would pick a different gateway (as far as .100.1 is concerned). How that works is beyond me but I know it can be done, it's what decent routers like the Draytek I have now will do, it's also what some Linux distros will do (I'm now playing with ClearOS which seems to have this functionality), and I have also found some scripts for setting it up (but they're more detailed than I was able to follow).
But they all seem to expect each gateway to reside on its own network interface, so if I want to have 3 WAN options for gateway then I need 3 network interfaces (plus another for the internal side). That's the bit I don't understand, and I feel like there must be a reason (otherwise they'd work the way I describe) but I can't find out what that reason would be.