On Sun, Aug 07, 2005 at 12:48:46AM +0200, Miroslav Kubik wrote:
> Thanks but this information did not help me. We have problem since afternoon
> and I need to solve this trouble as fast as possible so I can't afford to
> wait for the book.

You already have the proper keywords to search for on the net,
'arp' and 'poisoning'. The common remedy is to use static ARP
entries (man arp). If you were in a rush, it would take you
perhaps under a minute to find the answer on google.

sven