"But not every switch and network component works with 802.1x ... if you have some legacy equipment in your environment that may be a few years old chances are it may not have .1x capability.

"Today 802.1x itself needs extra code extensions and Cisco has put extensions of a standard for authentication and to move information between end points, policy and remediation servers across the network."

Bittinger said the existing standards cannot do what is required and the extension has yet to be accepted as a valid open standard, adding that in some recent deployments of VOIP, the 802.1x network has broken down.

"Both VOIP and NAC have to play well together to make it work and with Cisco telephones and networking gear [it's] not a problem, but with non Cisco phones using the 802.1x gear it breaks."

Bittinger emphasized the overlap between Cisco and Microsoft is obvious with NAC as both will offer policy servers and end point agents (Cisco through the Cisco Trusted Agent and Microsoft in Vista).