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Re: Controlling HTTP & SMTP IP flow for 3 NIC's

Craig White wrote:
On Wed, 2008-01-23 at 09:53 -0800, Tim Alberts wrote:
A little background first..I run 2 servers, mail and web. The mail server is down for hardware problems. I'm running both email and web on one server. The web server has 3 network interfaces 1 for public email, 1 for public web, and 1 for private network. I use 3 cards because the router I connect to the internet won't recognize multiple IP's for a single hardware MAC.

The problem is, that my email messages seem to be going out the web network interface. This is typically not a problem except for the reverse DNS lookup fails which at least one domain (Comcast.Net) rejects.

My question therefore is, how can I route my sendmail traffic to go out the correct ethernet interface? I'm sure I'll need to do the same for the web traffic so web site spoofing alarms are triggered.

I have told sendmail to listen to the correct interfaces, but that apparently doesn't mean only write to those interfaces. I don't see how to control this by setting up my routes and I can only really think of ways to block it in IPtables, not re-route it.
assuming that /etc/sysconfig/network has GATEWAY=SOME_IP_ADDRESS then
adding GATEWAYDEV=eth0 (or whatever) should identify which to use.


Craig, thank you for replying. However I don't think you understand. The system is routing, but I need to be able to route by port, not just IP.

Email is on one IP, web is on another IP, both on the same network, going through the same gateway to the internet. I have to do this because the gateway doesn't recognize virtual IP on the same hardware MAC.

I need to configure the Linux system to send smtp traffic (port 25) to eth2 and web traffic (port 80) web traffic to eth1. Both route to the same gateway ISP router.

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