Not all countries and regions have infrastructures for all WAN technologies. Therefore, your selection of WAN options might be limited by what is available. For example, X.25 might be the only WAN option supported in your country. If you are uncertain about your WAN options, contact the WAN service provider in your area. If you decide to use a synchronous leased line or an asynchronous dial-up line, you must also decide what type of WAN encapsulation to use.
Encapsulation is the wrapping of data in a particular protocol header.
The type of router that you are connecting to the Cisco 805 router determines the type of WAN encapsulation. This section discusses the features used in the sample networks. You can choose not to use features presented in the sample networks or add or substitute features that better suit your needs. In this situation, a dynamic routing protocol would advertise the small office network routes to the Internet, which is undesirable. With NAT, the Cisco 805 router translates the nonregistered IP addresses used by the small office network hosts into the globally unique IP address used by the serial interface when they access the Internet or vice versa.