CompTIA Network+® Study Guide

15.7. VPN Concentrators

A VPN concentrator is a device that creates remote access for virtual private networks (VPNs) either for users logging in remotely or for a large site-to-site VPN. In contrast to standard remote-access connections, remote-access VPNs often allow higher data throughput and provide encryption. Cisco produces VPN concentrators that support anywhere from 100 users up to 10,000 simultaneous remote-access connections.

Encryption for a remote-access VPN through a concentrator is usually handled by Internet Protocol Security (IPSec) or by Secure Sockets Layer (SSL), and user authentication can be achieved via Microsoft's Active Directory, Kerberos, Remote Authentication Dial In User Service (RADIUS), Rivest, Shamir, and Adleman ...