The NAS establishes an encrypted tunnel to the enterprise's private network. NAS-initiated VPNs allow remote users to connect to multiple networks using multiple tunnels. Because the Cisco Secure VPN Client is not required for a NAS-initiated access VPN solution, it is not a component of this network. The disadvantage of NAS-initiated access VPNs is that the PSTN is not secured. NAS-Initiated Access VPN Intranet VPNs Intranet VPNs connect corporate headquarters, remote offices, and branch offices over a shared infrastructure using dedicated connections.
Intranets are networks for businesses that are internal to the companies.
Intranets deliver the most current information and services available to networked employees. Intranets also increase employees' productivity by allowing for a reliable connection to consistent information. With an intranet VPN, you get the same security and connectivity for a corporate headquarters, remote offices, and branch offices as you would have with a private network. Figure 1-3 shows an intranet VPN topology. Also, the Cisco Secure VPN Client is not necessary for secure encryption over an intranet between two networking devices-an IPSec tunnel will suffice.