The initiative is intended to get Cisco's Network Admission Control (NAC) and Microsoft's Network Access Protection (NAP) to interoperate, so that external users connecting back to the network are verified and do not compromise security.
The technology works by ensuring that machines logging-on to a network are secure before being allowed access, keeping the network safe when users have been working outside the office.
Instead of Microsoft and Cisco customers facing a choice between NAP or NAC, they can now choose the components, infrastructure and technology from each to create a hybrid solution that is 'guaranteed' to work.
The partners have also set out a road map for bringing NAC and NAP to market, including a limited beta programme to start later this year.
However the full NAC/NAP solution will not be fully up and working until Longhorn is available some time in the second half of 2007.
Zeus Kerravala, vice president of security and networking research at Yankee Group, said: "This is exactly what is needed as businesses attempt to implement a network access control infrastructure to increase security amid an increasingly mobile workforce and an increasingly aggressive threat environment.
"Microsoft and Cisco must work together on this, and I'm pleased to see the two companies making the investment and the engineering commitment to interoperability."
Both firms are demonstrating the new architecture at the Security Standard conference, which opened yesterday in Boston.
Microsoft has published a white paper which describes the architecture and provides details on how to integrate the embedded security capabilities of Cisco's network infrastructure with those of Vista and Longhorn.
- Cisco Network Admission Control and Microsoft Network Access Protection Interoperability Architecture (PDF)