How to find users behind the router in LAN

Hi all,

I have small lan network, and I on my linux I must prevent access from
computers behind routers (linux or rest of the world), is there any
posibility to find out who is behind the router.

thanx in advance.

Where are your routers? Is your linux box a TCP/IP gateway?
If you provide TCP/IP routing (or NAT) service for your
subnet, and you don't want other users on your subnet to
further provide access (NAT) to others (subnets), the answer
is: you have no way to prevent that, unless you have control
over your user machines, and not enabling routing and/or NAT
on them.

My 2 cents.

Stephen Wong @ Hong Kong.D

On Tue, 24 Feb 2004, goody wrote:

> Hi all,
>
> I have small lan network, and I on my linux I must prevent access from
> computers behind routers (linux or rest of the world), is there any
> posibility to find out who is behind the router.
>
> thanx in advance.
>
>
>

On Tue, 24 Feb 2004 08:19:07 +0100, goody <mk-(E-Mail Removed)> wrote:
> Hi all,
>
> I have small lan network, and I on my linux I must prevent access from
> computers behind routers (linux or rest of the world), is there any
> posibility to find out who is behind the router.

If you are asking if there is a way to determine if someone connecting to
you from the internet is behind a router, the answer is everyone (internet
routers). Whether they are behind NAT or masquraded or using a proxy is
another matter. But why does it matter and how is that any different from
an unknown user from dynamic IP? If it matters, authenticate them.

ISPs can sometimes tell the number of active computers behind a cheap
broadband router by monitoring traffic and sequence numbers in different
types of traffic. But Linux masquerade uses random sequence numbers
making that much more difficult to determine. It would certainly be
unreliable for a single connection.

--
David Efflandt - All spam ignored http://www.de-srv.com/