2 Nics - Pass traffic through 1 out the other

[alienprdkt]

What we are trying to do is setup a nTop bandwidth monitoring server. Place this server between router and firewall. I want all LAN traffic to go through the nTop server on one NIC, and out to the router on the other NIC. Any suggestions on how I can accomplish this.

Having very bad internet issues due to traffic, need to see whats happening.

Thanks in advance,

[Jason0885]

I did something similar to this with IP Tables. This is what I done.
The setup is using CENTOS 5.6, it is a basic pppoe conenction. The modem was in bridging mode. I bridged the pppoe interface and the eth1 interface. eth1 went to a wireless hotspot.

In terminal type
1.) sudo iptables -A INPUT -i lo -j ACCEPT

2.) sudo iptables -A OUTPUT -o lo -j ACCEPT

3.) sudo iptables --table nat --append POSTROUTING --out-interface <interface> -j MASQUERADE

<interface> is your output interface. IE the one for your router. In my case eth1. Do not use the < and > signs if your if is eth1 just put eth1.

4.) sudo service iptables save

5.) Sudo nano /etc/sysctl.conf
nano is the name of your text editor. I used nano for this machine.

6.) Add the following line to enable packet forwarding for IPv4:
net.ipv4.conf.default.forwarding=1

Save the file

sudo service network restart

When the computer reboots you may have to restart iptables by running
sudo service iptables restart

It should be similar, or even the same way. It should be at least in the right direction. I believe the term is called MASQUERADEING.

Good luck, I hope this helps.