The convenience and advantages of secure VPNs has driven the specific technology to keep evolving continuously. Several years ago we only had the standardized IPSec VPN (which still strongly exists today). IPSec is a pure IP network VPN technology for connecting distant LAN networks over unsecured paths. Also, IPSec is used for client VPNs connecting remote teleworkers to their central site network. The characteristic of IPSec VPNs is that it provides FULL network connectivity between the VPN peers. That is, a remote access client IPSec VPN will connect the remote user to the central network just like the user would be locally connected.
After IPsec, the Web SSL VPN made its appearance. The remote user needs just a Web Browser with HTTPs to connect to the central site network. After authentication, the user is presented with a Web portal with links to the applications he is allowed to run. That is, the Web SSL VPN does not provide full network visibility to the remote user. The user has access only to specific applications (like internal email, internal files etc). Both IPSec VPNs and SSL VPNs are supported by Cisco ASA 5500 firewalls.
The newest generation of remote access VPNs is offered from Cisco AnyConnect SSL VPN client. This is supported by Cisco ASA 8.x. The AnyConnect SSL VPN provides the best features from both of the other VPN technologies (IPSec and Web SSL). With AnyConnect, the remote user has full network connectivity to the central site. Also, it offers the convenience of the Web SSL since there is no need to install an IPSec VPN client permanently to the user’s computer. Instead, there is an SSL client stored in the ASA flash memory which is downloaded to the remote user’s computer on demand.
How AnyConnect SSL VPN Client works
For first time user connection, the remote teleworker just opens a browser pointing to https://<ASA-outside-public-IP>. The browser connects to the ASA firewall and presents the user with a login screen. The user enters his credentials (username/password) and the ASA identifies that the user does not have the SSL client installed. Therefore it pushes the SSL client to the user’s computer. The client installs itself to the remote PC and establishes a secure SSL VPN connection between the remote user and the ASA. The user is also assigned an IP address from an address pool configured on the ASA and has full network access to the central site. When the SSL connection is stopped, the SSL client either uninstalls itself or remains on the user’s PC (depending on the configuration of the ASA).
In the case of a previously installed client, when the user authenticates, the security appliance examines the revision of the client, and upgrades the client as necessary.
The AnyConnect SSL client can be downloaded from the security appliance, or it can be installed manually on the remote PC by the system administrator.
In another post I will explain how to configure the AnyConnect SSL VPN on a Cisco ASA 5500 firewall.