I have often encountered the myth that VLANs are insecure and should not be used. People who state this proceed to buy a separate switch for each LAN that they deploy. Great commission for the salesman, but bad for the business paying the premium for the extra tin!A closer questioning of this reasoning exposes the myth that these people believe VLANs leak. My perception is that the root of this myth is a poor analysis done yonks ago and published on SANS, Intrusion Detection FAQ: Are there Vulnerabilities in VLAN Implementations? VLAN Security Test Report. This dated reports states as a recommendation: "Try not to use VLANs as a mechanism for enforcing security policy. They are great for segmenting networks, reducing broadcasts and collisions and so forth, but not as a security tool." This report is used as the basis of many flawed recommendations, see this thread. VLANs are a security tool but they are not an exclusive security tool!
VLANs are not an alternative to a firewall. Duh! VLANs are not an alternative to a router either. Duh! Firewalls (or routers) are not an alternative to VLANs. Duh! But not using VLANs, period, is short sighted and flawed. Not using VLANs is a larger risk than actually using them! Without using VLANS, it is not possible to implement a reasonably secure network design. Security is in the design and configuration, not the components! VLANs don't leak and I challenge any security bunnies out there, to provide documented proof of a successful exploit!
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