Dual WAN Ubuntu Router
I'm thinking of setting up a Ubuntu Server box as a router.
I have about 10 machines on my LAN which host various things (http, ftp and other servers) and I'm connected to two different ISPs.
From what I've figured I need a machine with 3 NICs and a Gigabit Switch (I already have this one). Now on the Ubuntu box I would have one card for each ISP and one for my LAN.
The problem I'm afraid I will encounter is that the servers (http,ftp etc.) won't be accessible from both ISPs because the machines that host the servers have only one gateway.
I would need to forward the same ports (80,21) to the same machine. I suppose that my Ubuntu box would simply forward the requests from both outside interfaces (from each ISP) to the correct machines inside but the responses from the machines would go out in the Internet through only one interface (which is the default gateway on the machine from the LAN).
If I were to use SNAT...would the packets follow the right path (my guess is yes but I haven't used it before so I'm not sure) Would I need two local interfaces for this (one for each WAN connection)? . Anyway using SNAT would mean the servers would think that all the connections are coming from the same IP (the local IP of my Ubuntu Box which is also the default gateway) - so this would render useless any logs or "visits" page.
How do DualWan routers achieve this?
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