Crash Course: VPNs

Get the lowdown on virtual private networks (VPNs) and learn how they can help your remote workers.

The VPN is one of the networking pro's most valuable tools for increasing network flexibility and providing user...

access. Learn about them fast in our Crash Course.


A virtual private network (VPN) is a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same capabilities, but at a much lower cost.

A VPN works by using the shared public infrastructure while maintaining privacy through security procedures and tunneling protocols such as the Layer Two Tunneling Protocol (L2TP). In effect, the protocols, by encrypting data at the sending end and decrypting it at the receiving end, send the data through a "tunnel" that cannot be "entered" by data that is not properly encrypted. An additional level of security involves encrypting not only the data, but also the originating and receiving network addresses.

Read the full definition here, courtesy of


Industry welcomes next-gen TLS VPN (21 Apr 2005|

Cisco discloses VPN Concentrator flaw (31 Mar 2005|

F5 ignites competition with updated FirePass VPN (18 Jan 2005|

Read more VPN-related news here.


VPN troubleshooting
This tip discusses two common issues associated with VPN services and suggests resolutions that can be handled by end users.

Check IT List: Choosing the right remote-access VPN
This tip discusses five questions to ask before you go procure and implement a VPN for your small or midsize business.

VPNs for wireless devices
Issues encountered when combining VPNs for wireless devices and WEP are covered by this tip.

DNS for VPNs
This tip from an Informit article on building Linux VPNs examines how to properly set up DNS for your VPN.

Read more VPN-related tips here.


How do I set up a VPN to connect several offices and the headquarters?
Expert response: This short excerpt from an Informit article on building Linux VPNs examines how to properly set up DNS for your VPN.

Configuring a Cisco router to work as a VPN
Expert response: Almost all 2600 series routers are able to terminate a VPN tunnel, whether there's a client on the other side using the Cisco VPN Client or...

Why can't I connect to Internet or local network while on the VPN?
You problem is fairly easy to resolve if you have administrative access to the remote VPN server you are connecting to or are able to communicate with its administrator.

View previously answered VPN-related Q&As here.


Migrating to IP-based VPNs
Enterprise VPNs have traditionally been deployed over leased lines using Frame Relay or ATM, but many enterprises are migrating their VPN infrastructure to IP using protocols such as IPsec, MPLS and SSL. Find out more about the options so that you can choose which is best for your network.

Secrets of Broadband VPNs for Remote Sites
Many enterprises in retail, financial services, and insurance, as well as other industries, are interested in making the move from frame relay, dialup, or VSAT, to broadband VPN to reduce cost and improve performance for their remote sites. Learn how with this webcast.

Remote Access: How to be both secure and productive
Most companies will need some form of both client-based VPN access in addition to clientless web-based SSL access in order to truly enable employees. Join us for an in depth discussion of how to make simple anywhere, anytime access a reality while maintaining the security that is necessary.

View more VPN-related webcasts here.


3-in-1 SSL VPN Decision Toolkit
Delivering clientless secure access to remote users across your enterprise is increasingly important. Your employees and partners now demand access to more applications, from more riskier places, using more devices. Different remote access technologies serve different needs, and it can be difficult to choose the one that precisely meets your company's requirements. Aventail's "SSL VPN Decision Toolkit" provides some vital information to help you at each stage of your decision process.

Building VPNs with IPsec and MPLS
This paper covers three types of VPNs: remote access, site-to-site, and firewall-based (a site-to-site variation). The variation between remote access and site-to-site VPNs will become more ambiguous as new devices such as hardware VPN clients, become more prevalent. These appear as a single device accessing the network, albeit there may be a network with several devices behind it. In all cases, the VPN comprises two endpoints that may be represented by routers, firewalls, client workstations, or servers.

Deploying IPsec virtual private networks
This white paper outlines IPSec in detail and provides a comprehensive deployment guide with multiple designs for the implementation of IPsec VPN configurations over public Internet infrastructure.

Read more VPN-related white papers here.

This was last published in September 2005