1. - 浙江邮电职业技术学院 - PPP 协议 《网络互联技术》 计算机通信教研室 周成纲 点到点协议

2. 2 教学目标（ Objectives ） 1. PPP 组成（ PPP Components ） 2. PPP 会话建立（ PPP Session Establishment ） 3. PPP 认证（ PPP Authentication ） 4. PAP 和 CHAP 配置（ Configure CHAP and PAP ） 5. 验证 PPP （ Verify PPP configuration ）

3. 3 专线 Leased Line 同步串行线路（ Synchronous serial ） Telephone Company 电路交换 Circuit-switched 异步串行线路 Asynchronous serial, ISDN Layer 1 Service Provider 分组交换 Packet-switched Synchronous serial 广域网连接类型：第一层 （ WAN Connection Types: Layer 1 ）

4. 4 串行线路点到点连接 （ Serial Point-to-Point Connections ） Router connections EIA/TIA-232EIA/TIA-449EIA-530V.35X.21 CSU/ DSU End user device Service Provider DTE DCE

5. 5 专线 （ Leased Line ） 电路交换 （ Circuit-switched ） PPP, SLIP, HDLC HDLC, PPP, SLIP 包交换 （ Packet-switched ） X.25, Frame Relay, ATM 第二层典型的广域网封装协议 （ Typical WAN Encapsulation Protocols: Layer 2 ） Telephone Company Service Provider

6. 6 HDLC 命令（ HDLC Command ） Router(config-if)#encapsulation hdlc HDLC 是串行线路的默认封装 HDLC is the default encapsulation on synchronous serial interfaces

7. 7 PPP 组成（ PPP Components ） 1. HDLC PPP 用 HDLC 作为点到点链路上基本的封装方法. PPP uses (HDLC) as a basis for encapsulating datagrams over point-to-point links. 2. LCP 建立、配置和测试数据链路的连接 Establishing, configuring, and testing the data-link connection. 3. NCP 建立和配置不同的网络层协议 Establishing and configuring different network-layer protocols.

8. 8 PPP Encapsulation TCP/IP Novell IPX AppleTalk Multiple protocol encapsulations using NCPs in PPP PPP 用 NCP 进行多种协议的封装 PPP can carry packets from several protocol suites using Network Control Programs PPP 用 LCP 进行链路的建立与控制 PPP controls the setup of several link options using LCP Link setup and control using LCP in PPP PPP 组成（ PPP Components ）

9. 9 Synchronous or Asynchronous 物理介质（ Physical Media ） 链路控制协议（ Link Control Protocol ） Authentication, other options 网络控制协议（ Network Control Protocol ） PPP Data Link Layer Physical Layer Network Layer IPCPIPXCP Many Others IPIPXLayer 3 Protocols PPP 各层元素（ Layering PPP Elements ）

10. 10 PPP 会话建立（ PPP Session Establishment ） 1. 链路的建立和配置的协商 Link establishment and configuration negotiation 2. 链路质量检测 Link-quality determination 3. 网络层协议配置协调 Network-layer protocol configuration negotiation 4. 链路终止 Link termination

11. 11 密码明文传输 Passwords sent in clear text 对方控制连接请求 Peer in control of attempts PPP 验证协议 --PAP （ PPP Authentication Protocol---PAP ） Remote Router (SantaCruz) Central-Site Router (HQ) Hostname: santacruz Password: boardwalk username santacruz password boardwalk PAP 2-Way Handshake “santacruz, boardwalk” Accept/Reject PAP :Password Authentication Protocol

12. 12 PPP 验证协议 --CHAP （ PPP Authentication Protocol---CHAP ） Remote Router (SantaCruz) Central-Site Router (HQ) Hostname: santacruz Password: boardwalk username santacruz password boardwalk CHAP 3-Way Handshake Challenge Response Accept/Reject 密文方式传递密码 Use “secret” known only to authenticator and peer 有效避免再生攻击和尝试攻击 Avoiding playback or repeated trial-and-error attacks CHAP :Challenge Handshake Authentication Protocol

13. 13 配置 PPP （ Configuring PPP ） Router(config-if)#encapsulation ppp 在端口模式下启动 PPP Enable PPP encapsulation

14. 14 配置 PPP 认证 （ Configuring PPP Authentication ） Router(config)#hostname name 指定你自己路由器的主机名 Assigns a host name to your router Router(config)#username name password password 确认被认证路由器的用户名和密码 Identifies the username and password of uthenticating router

15. 15 配置 PPP 认证 （ Configuring PPP Authentication ） Router(config-if)#ppp authentication {chap | chap pap | pap chap | pap} 选择 PAP 还是 CHAP 作为认证协议 Enables PAP and/or CHAP authentication

16. 16 配置 CHAP 实例 （ Configuring CHAP Example ） hostname left username right password sameone ! int serial 0/0 ip address 10.0.1.1 255.255.255.0 encapsulation ppp ppp authentication CHAP hostname left username right password sameone ! int serial 0/0 ip address 10.0.1.1 255.255.255.0 encapsulation ppp ppp authentication CHAP hostname right username left password sameone ! int serial 0/0 ip address 10.0.1.2 255.255.255.0 encapsulation ppp ppp authentication CHAP hostname right username left password sameone ! int serial 0/0 ip address 10.0.1.2 255.255.255.0 encapsulation ppp ppp authentication CHAP Left router Right router PSTN/ISDN 注意 : 用户名是对方的, 密码一定要相同 区分大小写

17. 17 验证 PPP 认证 （ Verifying PPP Authentication ） 4d20h: %LINK-3-UPDOWN: Interface Serial0, changed state to up 4d20h: Se0 PPP: Treating connection as a dedicated line 4d20h: Se0 PPP: Phase is AUTHENTICATING, by both 4d20h: Se0 CHAP: O CHALLENGE id 2 len 28 from ”left" 4d20h: Se0 CHAP: I CHALLENGE id 3 len 28 from ”right" 4d20h: Se0 CHAP: O RESPONSE id 3 len 28 from ”left" 4d20h: Se0 CHAP: I RESPONSE id 2 len 28 from ”right" 4d20h: Se0 CHAP: O SUCCESS id 2 len 4 4d20h: Se0 CHAP: I SUCCESS id 3 len 4 4d20h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up 4d20h: %LINK-3-UPDOWN: Interface Serial0, changed state to up 4d20h: Se0 PPP: Treating connection as a dedicated line 4d20h: Se0 PPP: Phase is AUTHENTICATING, by both 4d20h: Se0 CHAP: O CHALLENGE id 2 len 28 from ”left" 4d20h: Se0 CHAP: I CHALLENGE id 3 len 28 from ”right" 4d20h: Se0 CHAP: O RESPONSE id 3 len 28 from ”left" 4d20h: Se0 CHAP: I RESPONSE id 2 len 28 from ”right" 4d20h: Se0 CHAP: O SUCCESS id 2 len 4 4d20h: Se0 CHAP: I SUCCESS id 3 len 4 4d20h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up debug ppp authentication successful CHAP output Left router Right router Service Provider

18. 18 配置 PAP 实例 （ Configuring PAP Example ） hostname left ! int serial 0/0 ip address 10.0.1.1 255.255.255.0 encapsulation ppp ppp pap sent-username left password cisco hostname left ! int serial 0/0 ip address 10.0.1.1 255.255.255.0 encapsulation ppp ppp pap sent-username left password cisco hostname right username left password cisco ! int serial 0/0 ip address 10.0.1.2 255.255.255.0 encapsulation ppp ppp authentication pap hostname right username left password cisco ! int serial 0/0 ip address 10.0.1.2 255.255.255.0 encapsulation ppp ppp authentication pap Left router Right router PSTN/ISDN 注意 : 用户名是对方的, 密码一定要相同 区分大小写

19. 19 思考题（ Questions ） 1 ．什么是 PPP ？ PPP 由哪 3 部分组成？ 2 ． PPP 的两种认证方法是什么？各有什么特点 ？ 3 ． PAP 采用几次握手？ CHAP 采用几次握手？