When would you need this: When your ISP gives you dynamic IP address upon each connection or you need to configure the router to obtain its interface IP address automatically.

Special Requirements: None.

When would you need this: When you want to create a secure tunnel to transfer data between two sites without the use of VPN concentrator or other security devices.

Special Requirements: The routers used must support IPSec. Most of Cisco routers do. Another need is that both sides use a static public IP address to connect to the Internet.

Some commands in the Cisco router configuration are just irreplaceable. The ‘show’ commands are the most widely used in Cisco routers. Here is a list of the 10 mostly used of these ‘show’ commands.

When would you need this: When you are creating a WAN link. And also when the other end of a WAN link is NOT a Cisco router. Point-to-Point Protocol can be used in synchronous, asynchoronous, HSSI, and ISDN links.

Special Requirements: None.

When would you need this: When you are using ISDN links between more than two nodes.

Special Requirements: The router should have ISDN interface(s).

When would you need this: When you have ISDN WAN link and you want the router to use it.

Special Requirements: The router should have BRI interface(s).