On Thu, 9 Oct 2003, Manuel Bouyer wrote:

> > arp info overwritten for 24.XX.XX.1 by 00:09:12:80:90:54
> > arp info overwritten for 24.XX.XX.1 by 00:09:12:80:90:8c
>
> 2 different boxes (or at last 2 different NICs) have been using the same IP

I recently taught a class where the provided internet access used some
type of router that automatically assigned itself IP addresses to become
the needed gateway.

In other words, someone could bring in a computer, plug in, and
immediately attempt to browse to a webpage without changing their system's
IP or gateway (default route) address.

And DHCP appeared to not be needed -- you could use the internet with your
own original IPs.

How can this be done with using NetBSD as the router? (Any tools to allow
NetBSD to listen to traffic and assume it should be the gateway, so
automatically configure an interface alias for it??)

I can't remember about DNS though, but I am sure it figured that out too
(which should be easy by simply redirecting the port 53 traffic to a local
DNS server).

Another part of their setup, is that they use a HTTP proxy, so you visit
any webpage, but at first it gives you its own local webpage, and then
your internet access is enabled. (So you have to visit a HTTP webpage
before using ssh out, for example.)

Has anyone implemented something like that too?

I often saw "arp info overwritten" messages in this BSD network that
was plugged into it, because I had a hub (instead of a switched network)
that everything was plugged into. My BSD box was supposed to be the NAT
gateway for the clients, but then the site's smart router automatically
assigned itself to my BSD box's IP address when it saw the systems all
attempting to route through that IP.

   Jeremy C. Reed
   http://bsd.reedmedia.net/