1. Wide Area Networks(WANs) Lecture Week 2

2. Point-to-Point Protocol (PPP) Accessing the WAN

3. WAN Encapsulation WAN technologies operate at both Physical and Data-link layers of the OSI models, and that higher-layer protocols such as IP are encapsulated when sent across the WAN link. A WAN is usually terminated on a Cisco device’s serial interface. Serial interfaces support a wide variety of WAN encapsulation types By default, a serial interface will utilize HDLC for encapsulation

4. Other supported encapsulations protocols SDLC PPP LAPB(Link Access Procedure, Balanced) Serial Line Internet Protocol (SLIP) - A standard protocol for point-to-point serial connections using TCP/IP. SLIP has been largely replaced by PPP. Frame-Relay X.25 ATM Note:- Regardless of the WAN encapsulation used, it must be identical on both sides of a point-to-point link

5. HDLC Encapsulation High-Level Data-link Control (HDLC) is a WAN encapsulation protocol used on dedicated point- to-point serial lines. Though HDLC is technically an ISO standard protocol, Cisco’s implementation of HDLC is proprietary, and will not work with other routers. HDLC is also Cisco’s default encapsulation type for serial point-to-point links. HDLC provides no authentication mechanism

6. PPP Encapsulation Point-to-Point Protocol (PPP) is a standardized WAN encapsulation protocol that can be used on a wide variety of WAN technologies, including: Dedicated point-to-point serial lines Asynchronous dial-up links ISDN

7. PPP has four components: Physical – standard for physical serial communication (such as EIA/TIA-232-C, V.35, ISDN, etc.). HDLC – for encapsulating packets into frames over serial lines. LCP – for establishing, maintaining, and terminating point-to-point links. NCP – allows multiple Layer-3 protocols (such as IP and IPX) to be encapsulated into frames.

8. PPP supports several features that standalone HDLC does not Authentication – secures the communication by forcing the sending/receiving devices to identify themselves with a username and password. PPP supports two forms of authentication – PAP and CHAP. Compression – improves efficiency on slow links. PPP supports two forms of compression: Stac and Predictor. Multilink – allows multiple channels to be bundled or trunked together to combine the bandwidth. The bundled channels are treated as one logical channel. Callback – provides security and billing services. Allows a client to first dial a PPP server, disconnect, and then have the PPP server call the client back.

9. PPP supports two methods of authentication, PAP and CHAP. PAP (Password Authentication Protocol) sends passwords in clear text, and thus does not provide much security. CHAP (Challenge Handshake Authentication Protocol) uses MD5 to apply an irreversible hash

10. Configuring Basic PPP To configure a serial interface for PPP encapsulation: Router(config)# int s0/0 Router(config-if)# encapsulation ppp To configure PPP authentication: Router(config)# hostname Router1 Router(config)# username Router2 password PASSWORD Router(config)# int s0/0 Router(config-if)# ppp authentication chap

11. configure pap authentication: Router(config)# int s0/0 Router(config-if)# ppp authentication pap To view the encapsulation configured on the interface: Router# show interface s0/0 To troubleshoot PPP authentication between two routers: Router# debug ppp authentication

12. Describe the Fundamental Concepts of Point-to-Point Serial Communication Describe the concept of serial communication as the basis of WAN technologies

13. Describe the Fundamental Concepts of Point-to-Point Serial Communication… Explain how two or more data streams are transported across a single physical connection using TDM

14. Describe the Fundamental Concepts of Point-to-Point Serial Communication… Define the location of the demarcation point relative to customer and service provider networks

15. Describe the Fundamental Concepts of Point-to-Point Serial Communication… Explain the terms DTE and DCE with relative to the location of devices in a network

16. Describe the Fundamental Concepts of Point-to-Point Serial Communication… Describe how high-level data link control (HDLC) uses one of three frame types to encapsulate data

17. Describe the Fundamental Concepts of Point-to-Point Serial Communication… Explain when and how to configure HDLC encapsulation on a router

18. Describe the Fundamental Concepts of Point-to-Point Serial Communication… Describe the procedure to follow when troubleshooting a serial connection

19. Describe Point-to-Point Concepts Describe PPP in terms of its use in WAN links

20. Describe Point-to-Point Concepts… Describe the general function of each layer of PPP architecture

21. Describe Point-to-Point Concepts… Define the three phases of PPP session establishment

22. Describe Point-to-Point Concepts… Explain the role of the LCP in PPP

23. Describe Point-to-Point Concepts… Describe the characteristics of NCP

24. Configure PPP on a Serial Interface… Explain the purpose of the commands used to configure and verify PPP connections

25. Configure PPP on a Serial Interface… Explain the output of the show interfaces serial command

26. Configure PPP on a Serial Interface… Explain the output of the debug ppp command

27. Configuring PPP with Authentication Differentiate between PAP and CHAP

28. Configuring PPP with Authentication… Outline the PPP encapsulation and authentication process on a flow chart

29. Configuring PPP with Authentication… Explain how to configure a PPP connection with authentication

30. Configuring PPP with Authentication… Explain the output of the debug ppp authentication command

31. Thank you