Re: prohibiting visitors from connecting to network

[procengaz () securityfocus com, netscape () securityfocus com, nt () securityfocus com]

Either set the DHCP Server to filter by MAC Address or require certificates.  Another option is to set up yet a 3rd 
VLAN that simply goes nowhere.  If your network is huge, filtering by MAC could be somewhat painful.  By requiring all 
internal users to use a VPN, external users (non-employees) would never obtain a connection