Chapter 3 -- PPP

1. Chapter 3 -- PPP PPP – A continuation of CCNA – Semester 4

2. DataLink (Layer 2) TCP/IP Protocols • SLIP - SLIP is a standard protocol for point-to-point serial connections, using TCP/IP. • SLIP was a predecessor of PPP. • PPP - PPP provides router-to-router and host-to-network connections over synchronousand asynchronous circuits, which can be either dialup or leased lines.

3. PPP Supports • Protocols – TCP/IP, AppleTalk, IPX • Essential features such as dynamic address allocation, PAP authentication, CHAP authentication, and Multilink PPP

4. HDLC • High-Level Data Link Control (HDLC) is the default encapsulation for ISDN and serial interfaces on a Cisco router. Although HDLC is a default encapsulation, Cisco's HDLC is not necessarily compatible with other vendors' HDLC implementations • PPP is a standard protocol – can be used with any vendor equipment

5. PPP Specifications • It is a standard – operates at OSI Layer 2 • Encapsulates Layer 3 datagrams with a specialized frame. • PPP defines the Link Control Protocol (LCP) • Once the LCP establishes the Layer 2 connection, the Network Control Protocol (NCP) takes over– frame includes protocol field • Each Layer 3 protocol has its own NCP. For example, IP's NCP is IPCP; IPX's NCP is IPXCP, and Appletalk's NCP is ATALKCP

6. Code • RTA(config)#interface async 2 • RTA(config-if)#encapsulation ppp

7. Remote Connections • Exec • Can dial in and take control of command line • Telnet • Access resources – network access • Can access printers, servers, etc. • PPP encapulation via asynchronous dialup connection

8. Commands • RTA(config)#interface async 1 • RTA(config-if)#encapsulation ppp • RTA(config-if)#async mode interactive • RTA(config)#line 1 • RTA(config-line)#autoselect ppp during-login • Will eliminate possibility of Exec session • Router(config-if)#async mode dedicated • Will ensure PPP runs on specified line

9. Programming Interface • RTA(config)#interface async1 • RTA(config-if)#ip address10.1.1.1 255.255.255.0 or • RTA(config-if)#ip unnumbered lo0 192.16.1.1 • RTA(config-if)#peer default ip address 10.1.1.1 • Assigns an address (usually host on same subnet) to the dial-in unit or • RTA(config-if)#peer default ip address pool NAME • Requires global command # ip local pool pool-name starting-address end-address.

10. LCP Configuration Options • Authentication • CHAP or PAP • Callback • Billing consolidation • Compression • Reduces size of frame - Stacker, Predictor, and Microsoft Point to Point Compression (MPPC) • Multilink PPP • load balancing functionality over multiple WAN links

11. Authentication Programming • Router(config)#username Romeo password Juliet • Router(config-if)#encapsulation ppp • Router(config-if)#ppp authentication pap • Router(config-if)#ppp pap sent-username GIN password RUMMY • Name and password are case sensitive • Dialer-map command tells each router what to do (suggest it be used) – see 3.2.2

12. Configuring CHAP • Router(config-if)#encapsulation ppp • Router(config-if)#ppp authentication chap • Router(config-if)#ppp chap hostname GIN • Router(config-if)#ppp chap password RUMMY • Remember that you will also have to configure a local username/password database, or point the router to the TACACS+ or RADIUS server that has that information. • Router(config-if)#ppp authentication pap chap

13. Callback • provides a client/server relationshipbetween the endpoints of a point-to-point connection • can be used to control access and toll costs between hosts • the calling router (the callback client) pases authentication information to the remote router (the callback server) • for PPP callback server disconnects, and then places a return call • Both routers on a point-to-point link must be configured for PPP callback – server/client

14. Configuration for Callback • Server(config)#username Client password itsasecret • Server(config)#map-class dialer DIALBACK • Server(config-map-class)#dialer callback-server username • Server(config-map-class)#exit • Server(config)#interface async 1 • Server(config-if)#ppp callback accept • Server(config-if)#dialer map ip 10.1.1.2 name Client class DIALBACK modem-script hayes56k broadcast 5556002

15. Client Configuration • Client(config)#interface async 1 • Client(config-if)#encapsulation ppp • Client(config-if)#ppp authentication chap • Client(config-if)#ppp callback request • Client(config-if)#dialer in-band • Client(config-if)#dialer-group 1 • Client(config-if)#dialer map ip 10.1.1.1 name Server modem-script hayes56k broadcast 5556001

16. Compression • CPU or Memory Intensive • Can impact router performance • Use only on slow lines • Use commands to show impact • Show process cpu • Show processes memory

17. PPP Multilink • Use MLP with applications in which bandwidth requirements are dynamic, such as remote LAN access applications for telecommuters or small office, home office (SOHO) environments • Creates bundles • RFC 1717 and 1990

18. MMP Features • Combine multiple physical links into one logical link (bundle) • Receive and reassemble upper-layer protocol data units (PDUs) • Receive PDUs of a negotiated size

19. Troubleshooting Commands • Show dialer • view the status of asynchronous dialup connections. • Debug PPP negotiation • troubleshooting the PPP LCP activities such as authentication, compression, and MLP • Debug PPP Authentication • output is limited to CHAP and PAP authentication • events.