2.2.5 PPP的LAPB和LQM
两种方法加强PPP链路质量：
-
平衡式链路接入过程（LAPB）数字模式协商 ppp reliablelink
-
链路质量监控（LQM） ppp quality
LQM发送链路质量报告（LQR）代替keepalive，只监视链路质量。
LAPB提供重传纠错功能，可以使用压缩，但不能使用MPPP。
LQM配置命令：
Ppp multilink percentage_of_successful_traffic
2.2.6 PPP的“big show”和“big D”
-
Show interface interface_name 提供物理端口状态
-
Show line x 提供物理状态和部分逻辑接口状态
-
Show ip route 验证PPP子网是否处在up 和active状态
-
Debug ppp negotiation 显示LCP协商过程，例2-6显示PPP会话过程
-
Debug ppp authentication 显示PPP认证错误
-
Debug dialer 用于拨号开始里的调试(这
例2-9 debug ppp negotiation命令结果
shanghai(config-if)# debug ppp negotiation
00:14:45: Se1/0 LCP: I CONFREQ [Closed] id 5 len 15
00:14:45: Se1/0 LCP: AuthProto CHAP (0x0305C22305)
00:14:45: Se1/0 LCP: MagicNumber 0x011842CD (0x0506011842CD)
00:14:45: Se1/0 LCP: Lower layer not up, Fast Starting
00:14:45: Se1/0 PPP: Treating connection as a dedicated line
00:14:45: Se1/0 PPP: Phase is ESTABLISHING, Active Open ＜－ppp negotiation begins
00:14:45: Se1/0 LCP: O CONFREQ [Closed] id 49 len 15
00:14:45: Se1/0 LCP: AuthProto CHAP (0x0305C22305)
00:14:45: Se1/0 LCP: MagicNumber 0x001866BC (0x0506001866BC)
00:14:45: Se1/0 LCP: O CONFACK [REQsent] id 5 len 15
00:14:45: Se1/0 LCP: AuthProto CHAP (0x0305C22305)
00:14:45: Se1/0 LCP: MagicNumber 0x011842CD (0x0506011842CD)
00:14:45: %LINK-3-UPDOWN: Interface Serial1/0, changed state to up
00:14:45: Se1/0 LCP: I CONFACK [ACKsent] id 49 len 15
00:14:45: Se1/0 LCP: AuthProto CHAP (0x0305C22305)
00:14:45: Se1/0 LCP: MagicNumber 0x001866BC (0x0506001866BC)
00:14:45: Se1/0 LCP: State is Open
00:14:45: Se1/0 PPP: Phase is AUTHENTICATING, by both ＜－CHAP begins
00:14:45: Se1/0 CHAP: O CHALLENGE id 3 len 29 from "shanghai" ＜－CHAP challenge
00:14:45: Se1/0 CHAP: I CHALLENGE id 2 len 28 from "beijing"
00:14:45: Se1/0 CHAP: Using hostname from configured hostname
00:14:45: Se1/0 CHAP: Using password from AAA
00:14:45: Se1/0 CHAP: O RESPONSE id 2 len 29 from "shanghai"
00:14:45: Se1/0 CHAP: I RESPONSE id 3 len 28 from "beijing"
00:14:45: Se1/0 PPP: Phase is FORWARDING, Attempting Forward
00:14:45: Se1/0 PPP: Phase is AUTHENTICATING, Unauthenticated User
00:14:45: Se1/0 CHAP: I SUCCESS id 2 len 4 ＜－CHAP OK
00:14:45: Se1/0 PPP: Phase is FORWARDING, Attempting Forward
00:14:45: Se1/0 PPP: Phase is AUTHENTICATING, Authenticated User
00:14:45: Se1/0 CHAP: O SUCCESS id 3 len 4 ＜－CHAP OK
00:14:45: Se1/0 PPP: Phase is UP
00:14:45: Se1/0 IPCP: O CONFREQ [Closed] id 5 len 10 ＜－IP Parameters
00:14:45: Se1/0 IPCP: Address 1.1.1.1 (0x030601010101)
00:14:45: Se1/0 CDPCP: O CONFREQ [Closed] id 5 len 4
00:14:45: Se1/0 IPCP: I CONFREQ [REQsent] id 3 len 10
00:14:45: Se1/0 IPCP: Address 1.1.1.2 (0x030601010102)
00:14:45: Se1/0 IPCP: O CONFACK [REQsent] id 3 len 10
00:14:45: Se1/0 IPCP: Address 1.1.1.2 (0x030601010102)
00:14:45: Se1/0 IPCP: I CONFACK [ACKsent] id 5 len 10
00:14:45: Se1/0 IPCP: Address 1.1.1.1 (0x030601010101)
00:14:45: Se1/0 IPCP: State is Open ＜－IP OK
00:14:45: Se1/0 CDPCP: I CONFREQ [REQsent] id 3 len 4
00:14:45: Se1/0 CDPCP: O CONFACK [REQsent] id 3 len 4
00:14:45: Se1/0 CDPCP: I CONFACK [ACKsent] id 5 len 4
00:14:45: Se1/0 CDPCP: State is Open
00:14:45: Se1/0 IPCP: Install route to 1.1.1.2
00:14:45: Se1/0 IPCP: Add link info for cef entry 1.1.1.2
00:14:46: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/0, changed state to up
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