IP Forwarding: Att: Mike Burger

menonrr_at_adelphia.net
Date: 09/15/04

  • Next message: Ryan Golhar: "Error in /etc/cron.daily"
    To: <redhat-list@redhat.com>
    Date: Wed, 15 Sep 2004 11:43:47 -0400
    
    

    Hello,

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

    [root@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

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