Networking/routing Issue

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I’ve been working on this for over a week. I don’t think its working the way it should.

Here’s what I’m trying to do:

I have a Windstream dsl router with wireless >
CentOS 6.8 server eth0 > > gateway
eth1 > > gateway
Switch > other computers and devices > gateway

I want to send all internal traffic through, all external traffic through, then back through

I did an iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE


Outside connectivity for all other computers and devices only works if eth0
is also connected to the router, server works Iptraf shows no traffic on eth1

Hope I haven’t confused you as I have thoroughly confused myself.


TE Dukes

4 thoughts on - Networking/routing Issue

  • way it traffic
    [Thomas E Dukes]
    The above needs a little clarification: all external traffic through >> all other computers and devices.

    eth0 is

  • In article <003101d205da$b35b9a20$1a12ce60$>, TE Dukes wrote:

    Assuming your subnet mask is, you have both interfaces on the same subnet, which won’t work. You have two options:

    1. Change the third number on the DSL router and on eth1, e.g.

    2. Change the third number on eth0 and all the other computers and devices.

    Either of the above options will work. Choose whichever gives you least hassle.

    You need to make sure that all of the other devices have the address of your server’s eth0 set as their default gateway. The server needs to have the address of the router as its default gateway.

    If the other devices want to get their addresses via DHCP (a good idea), you will need to run a DHCP server on your server machine, as they will be isolated from the router.

    You will also need to make sure IP forwarding is enabled on the server.

    Cheers Tony