Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Semester 4, v Chapter 4: Point to Point Protocol Curriculum Review Youngstown State University Cisco Regional Academy

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Disclaimer  This presentation is intended for review purposes by Cisco Networking Academy Program teachers and students only.  This presentation is not a substitute for careful study of the Cisco Academy curriculum.  Most of the text and graphics have been copied directly from the on-line curriculum, and remain the copyrighted property of Cisco Systems.  CCNA objectives are used for reviews.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Contents  Part 1: PPP  Part 2: PPP Session Establishment  Part 3: PPP Authentication

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Chapter Learning Objectives  You will be able to: –Describe the 3 main components of PPP. –Identify the fields of a PPP frame. –Describe the 4 phases of PPP establishment. –Describe the 2 methods of PPP authentication including their strengths and weaknesses. –Configure PPP including authentication on a router interface.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Part 1 Point to Point Protocol

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Point to Point Protocol  SLIP limited Internet growth. PPP replaces it.  PPP connects routers with the ability to provide: –Control of the data link setup. –Dynamic assignment of IP addresses. –Use of multiple network protocols. –Link configuration and link quality testing. –Error detection. –Negotiation options for network-layer addressing and data compression. –Synchronous and Asynchronous circuits.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program PPP Components  Three main components are: 1.HDLC (High-Level Data Link Control) Encapsulate datagrams for point-to-point links. 2.LCP (Link Control Protocol) Establishes, configures, and tests data-link connection. 3.NCP (Network Control Protocols) Allows simultaneous use of multiple layer 3 protocols.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Six Field of PPP Frame  Flag – Indicates beginning or end of frame.  Address – Standard broadcast address (ppp does not assign individual station addresses!)  Control – One byte; sets connection-less service.  Protocol – Identifies layer 3 protocol of frame.  Data – Default maximum length of 1500 bytes.  FCS – Extra characters added for error control.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Part 2 Session Establishment

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Four Phases of PPP Establishment  To establish communications over a point-to- point link, PPP use four distinct phases: 1.Link establishment and configuration negotiation. 2.Link-quality determination. 3.Network-layer protocol configuration negotiation. 4.Link termination.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Phase 1: Link Establishment  LCP must first open the connection and negotiate the configuration parameters before network layer datagrams can be exchanged. –Originating PPP node sends LCP frames to open the data-link layer. –LCP frames contain a configuration option field that allows negotiation of the use of options such as: Maximum Transmission Unit (MTU) Compression of certain PPP fields Data link authentication protocol.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program  Link is tested to determine whether the quality is good enough to bring up network-layer protocols.  After the link is established, an authentication protocol can be chosen to authenticate client or user workstation. –PAP Password Authentication Protocol Challenge –CHAP Handshake Authentication Protocol Phase 2: Link-Quality Determination

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Phase 3: Network-layer Protocol Configuration Negotiation  PPP devices send NCP packets to configure one or more network-layer protocols. –Datagrams from each network-layer protocol can then be sent over the link.  Check a router LCP and NCP states with the show interfaces command.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Phase 4: Link Termination  LCP can terminate the link at any time.  Usually done at the request of a user.  Can happen because of a physical event, such as the loss of a carrier or a timeout.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Part 3 PPP Authentication

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program PPP Authentication  PPP authentication phase is optional. –After the link has been established, The authentication protocol is chosen, The peer is authenticated. –Authentication takes place before the network-layer protocol configuration phase.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program PAP  Peer Authentication Protocol –Simple method for a remote node to establish its identity. –Two-way handshake. –Username/password pair is repeatedly sent by the remote node until authentication is acknowledged or the connection is terminated. –Not a strong authentication protocol. Passwords are sent across the link in clear text, No protection from repeated trial-and-error attacks.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program CHAP  Challenge Handshake Authentication Protocol –Periodically verifies the identity of the remote node, using a three-way handshake. This improves security over PAP. Protects against playback attacks through the use of a variable challenge value that is unique and unpredictable. –Passwords are encrypted.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Configuring PPP Authentication 1.Define username and password expected from remote router. Router(config)#username name password secret 2.Configure the interface for PPP encapsulation. Router(config-if)#encapsulation ppp 3.Configure PPP authentication. Router(config-if)#ppp authentication{chap|pap} 4.For IOS 11.1 or later, you must configure PAP on interface responding to PAP request. Router(config-if)#ppp pap sent-username username password password

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program CHAP Configuration  To simplify router CHAP configuration tasks: –Use the same host name on multiple routers. Remote users think they are connecting to the same router when authenticating. Configure the same host name on each router. Router(config-if)# ppp chap hostname –Use a password to authenticate an unknown host. Router(config-if)# ppp chap password

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program PPP Verification  Use the show interface command to check LCP and NCP states.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Summary  PPP most widely used WAN protocol.  Provides LCP and NCP to negotiate parameters.  PPP session has 4 phases: –Link establishment –Link quality determination –Network-layer protocol configuration –Link termination.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program Summary  Select PAP or CHAP authentication when configuring PPP.  PAP is not a strong authentication protocol.  CHAP provides protection against playback attacks by using a unique and unpredictable variable challenge value.  Configure the interface for PPP encapsulation by using the encapsulation ppp command.  Check PPP LCP and NCP states by using the show interfaces command.

Robert E. Meyers CCNA, CCAI Youngstown State University Cisco Regional Academy Instructor Cisco Networking Academy Program End