Re: Help proxy_arp

From: Edu (faramir_27@hotmail.com)
Date: 01/19/03 

From: faramir_27@hotmail.com (Edu)
Date: 19 Jan 2003 03:12:39 -0800

Yes, yes...I should explain more things about my problem:

My box has two ethernet interfaces, in one of them may appear a host
with any IP from 0.0.0.0 to 255.255.255.255 (of course, I mean any IP
but the reserved ones) and my box must act as a completely transparent
proxy for all of them. It's not easy, but many issues are solved.

These hosts will try to find their default gateways, DNS, etc. and my
box must respond with its own MAC address to all of ARP requests in
order to act as the gateway for all hosts (which, as I said, may have
any possible IP). Enabling proxy_arp it worked except for the fact it
sends ARP responses when a host is verifying that there's no other
host with the same IP. That's what I want to change.

Another problem I must solve is the fact that there may be duplicated
IPs, but this is another story.

Edu

efflandt@xnet.com (David Efflandt) wrote in message news:<slrnb2kfbk.fa7.efflandt@typhoon.xnet.com>...
> On Sat, 18 Jan 2003 19:26:15 +0100, Edu <eduardg@mat.upc.es> wrote:
> > Hi,
> >
> > I would like to change the default proxy_arp behaviour. I think that
> > enabling proxy_arp in a Linux box (echo 1 >
> > /proc/sys/net/ipv4/ethX/proxy_arp) makes it to response all ARP requests
> > with its own MAC address, but...
>
> Only for itself or other interface(s) it is proxy arp for.
>
> > many times, when a PC starts its network devices, it sends an ARP request to
> > check out that nobody has its same IP address, so... I'd want the Proxy_ARP
> > to ignore these requests but the rest.
>
> No 2 machines on the same subnet should have the same IP anyway, so this
> does not really make any sense. In other words if proxy_arp is enabled on
> eth0 with 192.168.1.0/255.255.255.0 network) and eth1 is
> 192.168.1.240/255.255.255.248 network, then no computer on eth0 can use
> IPs 192.168.1.240-.247. Proxy arp is kind of like a bridge that puts
> other interfaces on the same network that proxy_arp is enabled on, except
> eth1 in this case would not see 192.168.1.255 broadcasts from eth0. But
> eth0 should and would answer arp requests that come in on that interface
> for any IP on eth1.

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