Companies with locations spread across multiple sites often require secure communications between those sites. One option is to purchase multiple WAN connections to interconnect those sites. Sometimes, however, a more cost-effective option is to create secure connections through an untrusted network, such as the Internet. Such a secure tunnel is called a virtual private network (VPN). Depending on the VPN technology being used, the devices that terminate the ends of a VPN tunnel might be required to perform heavy processing. For example, consider a company headquarters location with VPN connections to each of 100 remote sites. The device at theh headquarters terminating these VPN tunnels might have to perform encryption and authentication for each tunnel resulting in a heavy processor burden on that device.
Although several router models can terminate a VPN circuit, a dedicated device, called a VPN headend, or VPN concentrator, can be used instead. A VPN headend device performs the processor-intensive process required to terminate multiple VPN tunnels. Figure 9-18 shows a sample VPN topology, with a VPN concentrator at each corporate location.
The term encryption refers to the capability of a device to scramble data from a sender in such a way that the data can be unscrambled by the receiver but not by any other party that might intercept the data. Because a VPN concentrator is able to encrypt data, it is considered to belong to a class of devices called encryption devices, which are devices (such as routers, firewalls, and VPN concentrators) capable of participating in an encryption session.
About The Author
Anthony Sequeira, CCIE No. 15626, is a Cisco Certified Systems Instructor (CCSI) and author regarding all levels and tracks of Cisco Certification. Anthony formally began his career in the information technology industry in 1994 with IBM in Tampa, Florida. He quickly formed his own computer consultancy, Computer Solutions, and then discovered his true passion-teaching and writing about Microsoft and Cisco technologies. Anthony joined Mastering Computers in 1996 and lectured to massive audiences around the world about the latest in computer technologies. Mastering Computers became the revolutionary online training company, KnowledgeNet, and Anthony trained there for many years. Anthony is currently pursuing his second CCIE in the area of Security and is a full-time instructor for the next-generation of KnowledgeNet, StormWind.com. Anthony is also a VMware Certified Professional.
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