> > Others have given you good answers, but I felt I could share some > insight on the matter.. > > The MAC address of a NIC is used by switches to send packets out the > right port - As soon as you add a routing element, all traffic to a > routed IP appears to be destined for the router, if one goes by the > MAC address in the packet. > > If the destination MAC were to be encoded in the packet, no switches > would be able to keep their internal tables sane, as it would be > flooded with MACs, all on the same port (the one connected to the > gateway). > > When a switch recieves a packet adressed to a MAC that doesn't appear > in the switch-internal list, the packet will be flooded (sent out on > all ports). Once a packet from that MAC passes through the switch, > that MAC will be added to the list, and future packets only leave that > one port. > > The main function of a switch is to keep irrelevant packets away from > hosts, but packets to unknown (to the switch) hosts get sent > everywhere, just like a Hub would do. > yes - thanks all, it appears its a cross network 'issue' thanks