DHCP security

[razk () smarteam com]

hello

i am looking for a solution of restricting unauthorised MAC addresses to be able to connect into our LAN. (Visitors 
etc.)
our main concern is that we have around 50 new VmWares coming up everyday and our network is flat without any vlans so 
we can't realy put them in a seperate network.

i was introduced to a solution on the port level of the switch but was wandering if there are any other solutions.

thanks.

Raz.