Multiple provider gateway

netboy · 11-20-2005, 11:10 PM

Hi all

I've built a Linux router/gateway for a network pictured below. The router has two providers.

Code:

                                                                 ________
                                          +------------+        /
                                          |            |       |
                            +-------------+ Provider 1 +-------
        __                  |             |            |     /
    ___/  \_         +------+-------+     +------------+    |
  _/        \__      |     if1      |                      /
 /             \     |              |                      |
| Local network - if0+ Linux router |                      |     Internet
 \_           __/    |              |                      |
   \__     __/       |     if2      |                      \
      \___/          +------+-------+     +------------+    |
                            |             |            |     \
                            +-------------+ Provider 2 +-------
                                          |            |       |
                                          +------------+        \________

Local network: 192.168.0.0/24
if0: 192.168.0.254

if1: 192.168.10.1
Provider 1 router: 192.168.10.254

if2: 192.168.20.1
Router 2 router: 192.168.20.254

Provider 2 is the "main" link for web access etc and Provider 1 is going to be dedicated for mail. At the moment though I haven't set any of this up, everything is simply being routed out through Provider 2.

What I want to achieve is if Provider 2 goes down, all local traffic gets routed and NAT'd out through Provider 1.

I also want to provide fallback for mail. So mail will come down and go out Provider 1, however if Provider 1 goes down, mail will need to come down Provider 2 and out Provider 2. The former is easily achieved through a secondary MX.

So having little experience with iptables and routing on Linux, I was wondering if someone can provide advice on what routes I'll need and the tools I need to use. Can it just be done with 'route' command or will I need 'ip' etc?

Thanks in advance.

fr_laz · 11-21-2005, 06:55 PM

Hi,

I think you should have a look at this link: http://lartc.org/howto/
Chapter 4.2. Routing for multiple uplinks/providers should answer a lot of your questions.
Even though it may not be the ultimate answer, it's definetly something you have to read.