CCNA Guide to Cisco Networking Fundamentals Fourth Edition

1. CCNA Guide to Cisco Networking Fundamentals Fourth Edition Chapter 11 PPP and Frame Relay

2. Objectives • Describe PPP encapsulation • Configure PPP encapsulation and its options • Describe and enable PPP multilink • Understand Frame Relay standards and equipment CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

3. Objectives (continued) • Describe the role of virtual circuits and performance parameters in Frame Relay • Understand the Frame Relay topologies • Understand the difference between multipoint and point-to-point configurations • Configure and monitor Frame Relay CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

4. PPP • PPP • Internet standard protocol defined in RFCs 2153 and 1661 • Provide point-to-point, router-to-router, host-to-router, and host-to-host connections • Considered a peer technology based on its point-to-point physical configuration • Commonly used over dial-up or leased lines to provide connections into IP networks • Serial Line Internet Protocol (SLIP) was the predecessor to PPP CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

5. PPP (continued) • PPP can be used over several different physical interfaces, including the following: • Asynchronous serial • ISDN synchronous serial • High-Speed Serial Interface (HSSI) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

6. PPP in the Protocol Stack • You can use PPP over both asynchronous and synchronous connections • At the Physical layer of the OSI reference model • Link Control Protocol (LCP) • Used at the Data Link layer to establish, configure, and test the connection • Network Control Protocols (NCPs) • Allow the simultaneous use of multiple Network layer protocols and are required for each protocol that uses PPP CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

7. PPP in the Protocol Stack (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

8. Frame Format • PPP is based on the High-Level Data Link Control (HDLC) protocol • The difference between PPP frames and HDLC frames is that PPP frames contain protocol and Link Control Protocol (LCP) fields • LCP • Described in RFCs 1548, 1570, 1661, 2153, and 2484 • Describes PPP organization and methodology, including basic LCP extensions CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

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10. Frame Format (continued) • LCP field of the PPP packet can contain many different pieces of information, including the following: • Asynchronous character map • Maximum receive unit size • Compression • Authentication • Magic number • Link Quality Monitoring (LQM) • Multilink CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

11. Frame Format (continued) • LCP link configuration process • Modifies and enhances the default characteristics of a PPP connection • Includes the following actions: • Link establishment • Authentication (optional) • Link-quality determination (optional) • Network layer protocol configuration negotiation • Link termination CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

12. Establishing PPP Communications • Involves the following actions: • Link establishment • Optional authentication • Network layer protocol configuration negotiation • The link establishment phase involves the configuration and testing of the data link • The authentication process can use two authentication types with PPP connections: PAP and CHAP CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

13. Establishing PPP Communications (continued) • PPP is an encapsulation type for serial interface communications • To configure a PPP connection, you must access the interface configuration mode for the specific interface you want to configure • After LCP has finished negotiating the configuration parameters • Network layer protocols can be configured individually by the appropriate NCP CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

14. Establishing PPP Communications (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

15. Establishing PPP Communications (continued) • Configuring PPP Authentication • Using authentication with PPP connections is optional • You must specifically configure PPP authentication on each PPP host in order for the host to use it • You can choose to enable CHAP, PAP, or both on your PPP connection, in either order CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

16. Establishing PPP Communications (continued) • Once you set the authentication type • You must still configure a username and password for the authentication • You must exit interface configuration mode and enter global configuration mode • Type username followed by the host name of the remote router • Then type password followed by the password for that connection • Confirming PPP Communications • With the show interface command CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

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18. Establishing PPP Communications (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

19. Frame Relay Standards and Equipment • Frame Relay • A packet switching and encapsulation technology that functions at the Physical and Data Link layers of the OSI reference model • A communications technique for sending data over high-speed digital connections • ITU-T and ANSI define Frame Relay • As a connection between the data terminal equipment (DTE) and the data communications equipment (DCE) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

20. Frame Relay Standards and Equipment (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

21. Frame Relay Standards and Equipment (continued) • The physical equipment that is used on a network may vary from one organization to another • Some routers have built-in cards that allow them to make WAN connections CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

22. Frame Relay Standards and Equipment (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

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24. Frame Relay Standards and Equipment (continued) • Frame Relay access device (FRAD) • Network device that connects to the Frame Relay switch • Also known as Frame Relay assembler/disassembler • Frame Relay network device (FRND) • The Frame Relay switch CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

25. Virtual Circuits • You can use Frame Relay with nearly any serial interface • Operates by multiplexing • Frame Relay separates each data stream into logical (software-maintained) connections • Called virtual circuits • Which carry the data transferred on the connection • Two types of virtual circuits • Switched virtual circuits (SVC) • Permanent virtual circuits (PVC) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

26. DLCI • Frame relay connections identify virtual circuits by Data Link Connection Identifier (DLCI) numbers • A DLCI number associates an IP address with a specific virtual circuit • DLCI numbers have only local significance • DLCI numbers are usually assigned by the Frame Relay provider • Most likely not the same on either side of the Frame Relay switch CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

27. Frame Relay Map • Frame Relay map • A table in RAM that defines the remote interface to which a specific DLCI number is mapped • The definition will contain a DLCI number and an interface identifier • Which is typically a remote IP address • The Frame Relay map can be built automatically or statically depending on the Frame Relay topology CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

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29. Frame Relay Map (continued) • Subinterfaces • Virtual interfaces associated with a physical interface • Created by referencing the physical interface followed by a period and a decimal number • For the purposes of routing, however, subinterfaces are treated as physical interfaces • With subinterfaces, the cost of implementing multiple Frame Relay virtual circuits is reduced • Because only one port is required on the router CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

30. LMI • LMI basically extended the functionality of Frame Relay by: • Making the DLCIs globally significant rather than locally significant • Creating a signaling mechanism between the router and the Frame Relay switch, which could report on the status of the link • Supporting multicasting • Providing DLCI numbers that are globally significant makes automatic configuration of the Frame Relay map possible CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

31. LMI (continued) • LMI uses keepalive packets to verify the Frame Relay link and to ensure the flow of data • Each virtual circuit, represented by its DLCI number, can have one of three connection states: • Active • Inactive • Deleted • The Frame Relay switch reports this status information to the Frame Relay map on the local router CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

32. Inverse ARP • In multipoint configurations • Routers use the protocol Inverse ARP to send a query using the DLCI number to find a remote IP address • As other routers respond to the Inverse ARP queries, the local router can build its Frame Relay map automatically • To maintain the Frame Relay map, routers exchange Inverse ARP messages every 60 seconds by default CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

33. Encapsulation Types • LMI has several different protocol encapsulation types that it can use for management communications • Cisco routers support these types of LMI encapsulation: • cisco • ansi • q933a • Cisco routers (using IOS Release 11.2 or later) can “autosense” the LMI type used by the Frame Relay switch CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

34. Encapsulation Types (continued) • The basic LMI type has three information elements: report type, keepalive, and PVC status • Information concerning the status of the virtual circuit: • New • Active • Receiver not ready • Minimum bandwidth • Global addressing • Multicasting • Provider-Initiated Status Update CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

35. Encapsulation Types (continued) • Split horizon • Routing technique that reduces the chance of routing loops on a network • Prevents routing update information received on one physical interface from being rebroadcast to other devices through that same physical interface • People also refer to this rule as nonbroadcast multiaccess (NBMA) • Can cause problems for Frame Relay routing updates • The best solution is to configure separate point-to-point subinterfaces for each virtual connection CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

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39. Performance Parameters • Service contract specifies parameters by which the connection is expected to function: • Access rate • Committed Information Rate (CIR) • Committed Burst Size (CBS) • Excess Burst Size (EBS) • Oversubscription CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

40. Congestion • Frame Relay switches attempt to control congestion on the network • When the Frame Relay switch recognizes congestion • Sends a forward explicit congestion notification (FECN) message to the destination router • In addition, the switch sends a backward explicit congestion notification (BECN) message to the transmitting, or source, router CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

41. Frame Format CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

42. Frame Relay Topologies • Frame Relay can use many different WAN topologies: • Peer (point-to-point) • Star (hub and spoke) • Partial mesh • Full mesh physical CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

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44. Frame Relay Configuration • In this section, you will learn how to configure Frame Relay over serial interfaces • Using IP as the Network layer protocol CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

45. Basic Multipoint Configuration with Two Routers • LMI will notify the router about the available DLCI numbers • Inverse ARP will build the Frame Relay map dynamically CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

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48. Basic Multipoint Configuration with Two Routers (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

49. Multipoint Configuration Using a Subinterface • The Frame Relay map will have to be built statically on RouterA • To configure a multipoint subinterface, you map it to multiple remote routers using the same subnet mask, but different DLCI numbers CCNA Guide to Cisco Networking Fundamentals, Fourth Edition

50. Multipoint Configuration Using a Subinterface (continued) CCNA Guide to Cisco Networking Fundamentals, Fourth Edition