Networking - Wide Area Network

PPP (Point to Point Protocol) is used on a Cisco network for router to router and host to network communications over synchronous and asynchronous circuits, including High Speed Serial Interface “Hissy” and ISDN interfaces. PPP works with several network protocols including IP, IPX, and ARA. PPP uses LCP an NCP protocols (Link Control Protocol, and Network Control Protocol).


Serial Ports can also be configured to support PPP interface. The port is allowed to emulate PPP encapsulation so that Cisco devices can communicate with non-Cisco devices. HDLC can be used for this also, but more often PPP is considered a better tool.


Security with PPP

PAP (Password Authentication Protocol) PAP is a basic security blanket for PPP. It asks for the username and password and if the router recognizes it then it sends back authorization acknowledgment.

CHAP (Challenge Handshake Authentication Protocol) CHAP is a inbound authentication method that allows the receiving device initiate a challenge sequence. That sequence is:

1. After connection is made the receiving device transmits a challenge message to the requesting device, the requesting device responds with an encrypted value using a one way math function.

2. The receiving device checks the response by comparing its value to the requesting devices value of the math function.

3. If the two values match then authentication is acknowledged and the connection continues.