Chapter 2 –PPP potx

Học viện mạng Bach Khoa - Website: www.bkacad.com 2Introducing Serial Communications • Computers make use of relatively short parallel connections between interior components, but use a

Trang 1

Chapter 2 – PPP

CCNA Exploration 4.0

Trang 2

Học viện mạng Bach Khoa - Website: www.bkacad.com 2

Introducing Serial Communications

• Computers make use of relatively short parallel connections between interior components, but use a serial bus to convert signals for most external communications.

Trang 3

• In a parallel connection, it is wrong to assume that the 8 bits leaving the sender

at the same time arrive at the receiver at the same time Rather, some of the bits get there later than others This is known as clock skew

Trang 4

• Parallel wires are physically bundled in a parallel cable, and signals can imprint themselves on each other The possibility of crosstalk across the wires

requires more processing, especially at higher frequencies

Trang 5

Trang 6

Trang 7

Parallel to Serial Conversion

Trang 8

TDM

Trang 9

STDM

Trang 10

TDM Examples

Trang 11

TDM Examples

Trang 12

TDM Examples

Trang 13

SERIAL POINT-TO-POINT LINK

Trang 14

HDLC Encapsulation

dedicated links, and circuit-switched connections when the link uses two Cisco devices HDLC is now the basis for synchronous PPP used

by many servers to connect to a WAN, most commonly the Internet.

Trang 15

Trang 16

Trang 17

Configuring HDLC Encapsulation

Trang 18

Introducing PPP

Trang 19

PPP Layered Architecture

Trang 20

PPP Architecture - Link Control Protocol Layer

Trang 21

PPP Architecture - Network Control Protocol Layer

Trang 22

PPP Frame Files

Trang 23

Establishing a PPP Session

Trang 24

Establishing a Link with LCP

Trang 25

The LCP Link Negotiation Process

Trang 26

LCP Packet

Trang 27

LCP Packet

Trang 28

PPP Configuration Options

Trang 29

Trang 30

NCP Explained

Trang 31

CONFIGURING PPP

Trang 32

Trang 33

PPP Configuration Commands

Trang 34

PPP Compression

Trang 35

IOS Supported Compression Methods

Trang 36

Configuring Compression

Trang 37

Link Quality Monitoring (LQM)

• Link Quality Monitoring (LQM) is available on all serial interfaces running PPP LQM will monitor the link quality, and if the quality drops below a configured percentage, the router shuts down the link

• The percentages are calculated for both the incoming and outgoing

directions

– The outgoing quality is calculated by comparing the total number of packets and bytes sent with the total number of packets and bytes received by the destination node

– The incoming quality is calculated by comparing the total number of packets and bytes received with the total number of packets and

bytes sent by the destination peer.

• When LQM is enabled, Link Quality Reports (LQRs) are sent, in place of keepalives, every keepalive period All incoming keepalives are

responded to properly If LQM is not configured, keepalives are sent

every keepalive period and all incoming LQRs are responded to with an LQR.

• LQR is specified in RFC 1989, PPP Link Quality Monitoring, by William

A Simpson of Computer Systems Consulting Services.

Trang 38

PPP Multilink

Trang 39

Extra: Configuring PPP Multilink

interface loopback 0

ip address 192.168.1.2 255.255.255.0

interface Virtual-Template1

ip unnumbered loopback0 ppp multilink

interface Serial0

no ip address encapsulation ppp ppp multilink interface Serial1

no ip address encapsulation ppp ppp multilink interface Serial2

no ip address encapsulation ppp ppp multilink

Trang 40

Extra: Configuring PPP Multilink

(config)# interface Multilink 1

ip address 1.2.3.4 255.255.255.0 ppp multilink

(config)# interface Serial 0/0

ppp multilink group 1 (config)# interface Serial 0/1

ppp multilink group 1

Trang 41

Configuring PPP

with Authentication

Trang 42

PPP Authentication Protocols

• The authentication phase of a PPP session is optional If used, you can authenticate the peer after the LCP establishes the link and choose the authentication protocol If it is used, authentication takes place before the network layer protocol configuration phase begins

Trang 43

Password Authentication Protocol (PAP)

Trang 44

Challenge Handshake Authentication Protocol (CHAP)

• Initiating CHAP

• Completing CHAP

Trang 45

Trang 46

Configuring PPP with Authentication

Trang 47

Trang 48

Notes:

- sent-username and password must match remote username and password

- Passwords are case-sensitive, but usernames are not

- Hostnames are not involved

Example: Configuring PAP

172.25.3.0/24 Serial 1/S0 2/S0

DCE DTE

interface Serial0

ip address 172.25.3.1 255.255.255.0 encapsulation ppp

ppp authentication pap ppp pap sent-username HQ

password HQpass

Trang 49

Extra: One-way PAP authentication

(config)# hostname RA

(config)# interface serial 0

encapsulation ppp ppp pap sent-username RA-X password CISCO-X

(config)# hostname RB (config)# username RA-X password CISCO-X (config)# interface serial 0

encapsulation ppp ppp authentication pap

Trang 50

Extra: Two-way PAP authentication

(config)# username RB-X password CISCO-B

encapsulation ppp ppp authentication pap ppp pap sent-username RA-X password CISCO-A

(config)# hostname RB (config)# username RA-X password CISCO-A (config)# interface serial 0

encapsulation ppp ppp authentication pap ppp pap sent-username RB-X password CISCO-B

Trang 51

Notes:

- Hostnames are involved unless the ppp chap hostname command is used, and

must match remote router’s username command (not case-sensitive)

- Passwords are case-sensitive and must match

Example: Configuring CHAP

172.25.3.0/24 Serial 1/S0 2/S0

DCE DTE

hostname SantaCruz

username HQ password boardwalk

ppp chap hostname SantaCruz (optional)

ppp authentication chap

Trang 52

Extra: One-way CHAP authentication

(config)# hostname RA-X

(config)# username RB password CISCO

encapsulation ppp OR

encapsulation ppp ppp chap hostname RA-X ppp chap password CISCO

(config)# hostname RB (config)# username RA-X password CISCO (config)# interface serial 0

encapsulation ppp ppp authentication chap

Trang 53

Verifying a Serial PPP Encapsulation Configuration

Trang 54

Troubleshooting PPP

Trang 55

Troubleshooting PPP Encapsulation

Trang 56

Troubleshooting PPP

Trang 57

Troubleshooting PPP Encapsulation

Trang 58

Troubleshooting a PPP Configuration with Authentication

• In the last line, the code = 4 means a failure has occurred Other code values are as

Trang 59

Troubleshooting a Serial Interface

• You can identify any of the following five possible problem states in the interface status line:

1 Serial x is down, line protocol is down

2 Serial x is up, line protocol is down

4 Serial x is up, line protocol is down (disabled)

5 Serial x is administratively down, line protocol is down

Trang 60

Trang 61

• The command syntax varies, depending on the platform Cisco 7000 series routers use a cBus controller card for connecting serial links

With these routers, use the show controllers cbus command

Trang 62

Trang 63

Trang 64

Trang 65

Tiêu đề	Introducing Serial Communications
Trường học	Học viện mạng Bach Khoa
Chuyên ngành	Networking
Thể loại	Lecture notes

Định dạng
Số trang	65
Dung lượng	2,48 MB