Introduction to Wide Area Networks (WANs): HDLC, PPP, and Frame Relay

1. Instructor & Todd Lammle Sybex CCNA 640-802 Chapter 14: Wide Area Networks

2. Chapter 14 Objectives The CCNA Topics Covered in this chapter include: • Introduction to WAN’s • HDLC • PPP • Frame Relay • Introduction to VPN’s 2

3. Defining WAN Terms • Customer Premises Equipment (CPE) • Demarcation (demarc) • Local loop • Central Office (CO) • Toll network

4. WAN Connection Types

5. DTE-DCE-DTE

6. WAN Support • Frame Relay • ISDN • LAPB • LAPD • HDLC • PPP • ATM

7. HDLC Protocol • Bit-oriented Data Link layer ISO standard protocol • Specifies a data encapsulation method • No authentication can be used

8. HDLC Frame Format

9. Point-to-Point Protocol (PPP) • Purpose: • Transport layer-3 packets across a Data Link layer point-to-point link • Can be used over asynchronous serial (dial-up) or synchronous serial (ISDN) media • Uses Link Control Protocol (LCP) • Builds & maintains data-link connections

10. Point-to-Point Protocol Stack

11. PPP Main Components • EIA/TIA-232-C • Intl. Std. for serial communications • HDLC • Serial link datagram encapsulation method • LCP • Used in P-t-P connections: • Establishing • Maintaining • Terminating • NCP • Method of establishing & configuring Network Layer protocols • Allows simultaneous use of multiple Network layer protocols

12. LCP Configuration Options • Authentication • PAP • CHAP • Compression • Stacker • Predictor • Error detection • Quality • Magic Number • Multilink • Splits the load for PPP over 2+ parallel circuits; a bundle

13. PPP Session Establishment • Link-establishment phase • Authentication phase • Network-layer protocol phase

14. PPP Session Establishment

15. PPP Authentication Methods • Password Authentication Protocol (PAP) • Passwords sent in clear text • Remote node returns username & password • Challenge Authentication Protocol (CHAP) • Done at start-up & periodically • Challenge & Reply • Remote router sends a one-way hash ~ MD5

16. Configuring PPP • Step #1: Configure PPP on RouterA & RouterB: Router__#config t Router__(config)#int s0 Router__(config-if)#encapsulation ppp Router__(config-if)#^Z • Step #2: Define the username & password on each router: • RouterA: RouterA(config)#username RouterB password cisco • RouterB: RouterB(config)#username RouterA password cisco NOTE: (1) Username maps to the remote router (2) Passwords must match • Step #3: Choose Authentication type for each router; CHAP/PAP Router__(Config)#int s0 Router__(config-if)#ppp authentication chap Router__(config-if)#ppp authentication pap Router__(config-if)#^Z

17. PPP Example 1

18. PPP Example 2

19. PPP Example 3

20. PPP Example 4

21. Frame Relay • Background • High-performance WAN encapsulation method • OSI Physical & data Link layer • Originally designed for use across ISDN • Supported Protocols • IP, DECnet, AppleTalk, Xerox Network Service (XNS), Novell IPX, Banyan Vines, Transparent Bridging, & ISO

22. Before Frame Relay

23. After Frame Relay

24. Frame Relay • Purpose • Provide a communications interface between DTE & DCE equipment • Connection-oriented Data Link layer communication • Via virtual circuits • Provides a complete path from the source to destination before sending the first frame

25. Frame Relay Terminology

26. Frame Relay Encapsulation • Specified on serial interfaces • Encapsulation types: • Cisco (default encapsulation type) • IETF (used between Cisco & non-Cisco devices) RouterA(config)#int s0 RouterA(config-if)#encapsulation frame-relay ? ietf Use RFC1490 encapsulation <cr>

27. Data Link Connection Identifiers (DLCIs) • Frame Relay PVCs are identified by DLCIs • IP end devices are mapped to DLCIs • Mapped dynamically or mapped by IARP • Global Significance: • Advertised to all remote sites as the same PVC • Local Significance: • DLCIs do not need to be unique • Configuration RouterA(config-if)#frame-relay interface-dlci ? <16-1007> Define a DLCI as part of the current subinterface RouterA(config-if)#frame-relay interface-dlci 16

28. DLCI’s are Locally Significant

29. Local Management Interface (LMI) • Background • Purpose • LMI Messages • Keepalives • Multicasting • Multicast addressing • Status of virtual circuits

30. LMI Types • Configuration: RouterA(config-if)#frame-relay lmi-type ? cisco ansi q933a • Beginning with IOS ver 11.2+ the LMI type is auto-sensed • Default type: cisco • Virtual circuit status: • Active • Inactive • Deleted

31. Sub-interfaces • Definition • Multiple virtual circuits on a single serial interface • Enables the assignment of different network-layer characteristics to each sub-interface • IP routing on one sub-interface • IPX routing on another • Mitigates difficulties associated with: • Partial meshed Frame Relay networks • Split Horizon protocols

32. Partial Meshed Networks

33. Creating Sub-interfaces Configuration: #1: Set the encapsulation on the serial interface #2: Define the subinterface RouterA(config)#int s0 RouterA(config)#encapsulation frame-relay RouterA(config)#int s0.? <0-4294967295> Serial interface number RouterA(config)#int s0.16 ? multipoint Treat as a multipoint link point-to-point Treat as a point-to-point link

34. Mapping Frame Relay Necessary to IP end devices to communicate • Addresses must be mapped to the DLCIs • Methods: • Frame Relay map command • Inverse-arp function

35. Using the map command RouterA(config)#int s0 RouterA(config-if)#encap frame RouterA(config-if)#int s0.16 point-to-point RouterA(config-if)#no inverse-arp RouterA(config-if)#ip address 172.16.30.1 255.255.255.0 RouterA(config-if)#frame-relay map ip 172.16.30.17 16 ietf broadcast RouterA(config-if)#frame-relay map ip 172.16.30.18 17 broadcast RouterA(config-if)#frame-relay map ip 172.16.30.19 18

36. Using the inverse arp command RouterA(config)#int s0.16 point-to-point RouterA(config-if)#encap frame-relay ietf RouterA(config-if)#ip address 172.16.30.1 255.255.255.0

37. Congestion Control • Discard Eligibility (DE) • Forward-Explicit Congestion Notification (FECN) • Backward-Explicit Congestion Notification (BECN)

38. Committed Information Rate (CIR) • Definition: Provision allowing customers to purchase amounts of bandwidth lower than what they might need • Cost savings • Good for bursty traffic • Not good for constant amounts of data transmission

39. Monitoring Frame Relay RouterA>sho frame ? ip show frame relay IP statistics lmi show frame relay lmi statistics map Frame-Relay map table pvc show frame relay pvc statistics route show frame relay route traffic Frame-Relay protocol statistics RouterA#sho int s0 RouterB#show frame map Router#debug frame-relay lmi

40. Troubleshooting Frame Relay Why can’t RouterA talk to RouterB?

41. Troubleshooting Frame Relay Why is RIP not sent across the PVC?

42. Introduction to VPN’s • VPNs are used daily to give remote users and disjointed networks connectivity over a public medium like the Internet instead of using more expensive permanent means. 42

43. Types of VPN’s • Remote access VPNs Remote access VPNs allow remote users like telecommuters to securely access the corporate network wherever and whenever they need to. • Site-to-site VPNs Site-to-site VPNs, or, intranet VPNs, allow a company to connect its remote sites to the corporate backbone securely over a public medium like the Internet instead of requiring more expensive WAN connections like Frame Relay. • Extranet VPNs Extranet VPNs allow an organization’s suppliers, partners, and customers to be connected to the corporate network in a limited way for business-to-business (B2B) communications. 43

44. Written Labs and Review Questions • Open your books and go through all the written labs and the review questions. • Review the answers in class. 44