IP Forwarding: Att: Mike Burger

[menonrr at adelphia.net]

Hello,

I did the 'ip addr' command. The result is as follows:

[root at localhost root]# ip addr
1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 brd 127.255.255.255 scope host lo

2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
    link/ether 00:60:97:df:8a:82 brd ff:ff:ff:ff:ff:ff
    inet 172.16.4.2/24 brd 172.16.4.255 scope global eth0

3: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
    link/ether 00:06:5b:b5:86:a9 brd ff:ff:ff:ff:ff:ff
    inet 172.16.3.10/24 brd 172.16.3.255 scope global eth1


Issue:

Is there a way so that I can forward the packets from the 172.16.4.0 network without having its IP address changed to 172.16.3.10, which is the so called "external interfce" for me.


Network set up: (Strictly private)

The redhat 9 gateway forwards traffic between two private networks. The network topology goes like this:

172.16.8.0/24 ------------ router ----------- 172.16.3.0/24 ------- | Redaht 9 | ------- 172.16.4.0/24

This is a strictly private network setup for doing some tests.


I had posted this question earlier:
-----------------------------------

Hello,

I am a fairly new person in Linux networking.

The issue I got some responses was as follows:
-------------------------------------------------------
I have had some good help to enable IP forwarding on my Redhat 9 
gateway with the rule:

[CODE]iptables -t nat -A POSTROUTING -o eth1 -j SNAT --to-source 172.16.3.10[/CODE] 

This rule forwards the traffic from the internal network (172.16.4.0/24) to the 
outside trhough the NIC with IP address 172.16.3.10.

Problem:

But I feel that the internal IPs are being forwarded with the IP address of the 
external NIC of the gateway.

It would be helpful if I could have a way to keep the internal IP address 
(172.16.4.0)as it is without being substituted with the gateways IP 
address(172.16.3.10). This is because I want the external users to see the 
internal machines(172.16.4.0 network) as it is.

Please advise.

Thank You.

Menon