proxy ARPing - was Re: [Wylug-help] Possible IP subnet conflict

[John Hodrien]

On Tue, 14 Jan 2003, Gary Stainburn wrote:

> I'm just about to set up a test system to try this out.
>
> I'm going to have a Linux box on my network with IP address 10.1.1.20/16 on
> eth0.
>
> It's going to have IP address 192.168.1.1/24 on eth1 connected via a
> cross-over to another Linux box pretending to be a pair of Cisco routers,
> then via another cross-over to a destination host on 10.1.0.34 pretending to
> be their web server.
>
> Questions:
>
> Which kernel version did you use?

2.4.18-19.7.x (Redhat 7.3)

> How do I set up the ARP proxying for 10.1.0.x?

in /etc/sysctl.conf:

net.ipv4.ip_forward = 1
net.ipv4.conf.eth0.proxy_arp = 1

eth0 is the outside world in my case, and eth1 is my enclosed subnet.  ARP
proxying has nothing to do with IP, since it's lower level.  It just echos
arp-requests and the like from one interface to another.  Otherwise when
someone is looking for a machine behind you firewall thang, noone will reply.
The request has to be passed to the inside so that they can reply.

> How can I NAT the traffic for 10.1.0.x and route it through the cisco box
> while not stuffing the rest of the 10.1.x.x network on eth0?

Shouldn't need to be NATted I don't think.  I'm somewhat confused by the
network description.  Can you do it again for my befuddled mind?

> (I need the traffic NATing so that the other end knows to return the traffic
> to my box)?

There's not necessarily any need to NAT.  I'm certainly not.

> Is this something I can configure into a Smoothwall/IPCOPs style distribution
> or do I need a cut-down RH dist for the job?

Assume you can do it with whatever, I just happened to have a RedHat box doing
nothing useful.

Sorry for that gibber, I've been a tad vague.

jh

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