Masq+IPs+server

From: Steven Kurylo <slug_at_no.spam.please>
Date: Sat Mar 24 2001 - 12:36:14 CST

I have had a question bothering me for a while now, and I am wondering if
any one here can explain it to me.

Below is a description of the setup. I randomly chose port 1000, if that
makes a difference I can look up which port the machine is actually using.

client is the user off in internet land making a request.
eth0 is the nic that ISP #1 is connected to on the linux masq machine.
eth1 is the nic that ISP #2 is connected to on the linux masq machine.
server is the machine that is listening for requests.

Request coming in

        client -> eth0:1000 (forwarded to) -> server:1000
                                        
Now the request coming back out

        server:1000 -> default gateway (masq machine) -> eth0:1000 -> client

So eth1 would look like

        client -> eth1:1000 (forwarded to) -> server:1000
        server:1000 -> default gateway (masq machine) -> eth0:1000 -> client

So would the above diagram work? Two seperate IPs, both forwarding port
1000 to a server that is listening and sending replies back out.

We were told (actually I wasn't there so I got the synopsis "it doesn't
work") that getting a second external net connection wouldn't work, as
shown in the diagrams above.

I can't figure why not. The only hang up I can see is that requests coming
in on eth1 are being sent back out on eth0 (because of the default
gateway). However in the wide world of the net, the packet should be able
to find its way home, yes?

Is there something am I missing? Could there be something in the software
on the server that would choke on this? Did the person who told this to us
be mistaken?

Thanks,

Steven

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Received on Sat Mar 24 12:36:14 2001

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