实验28:HDLC 和PPP 封装<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

1. 实验目的

通过本实验，读者可以掌握如下技能：

（1） 串行链路上的封装概念

（2） HDLC 封装

（3） PPP 封装

2. 实验拓扑

如图：

 

3. 实验步骤

注：
显示串行接口时，常见以下几种状态：

Serial0/0/0 is up, line protocol is up

//链路正常

Serial0/0/0 is administratively down, line protocol is down

//没有打开该接口，执行“no shutdown”可以打开接口

Serial0/0/0 is up, line protocol is down

//物理层正常，数据链路层有问题，通常是没有配置时钟、两端封装不匹配、PPP 认证错误

Serial0/0/0 is down, line protocol is down

//物理层故障，通常是连线问题

配置如下：
r0(config)#int s0/0

r0(config-if)#ip add 172.16.1.1 255.255.255.0

r0(config-if)#no sh

r0(config-if)#

*Mar  1 00:01:31.655: %LINK-3-UPDOWN: Interface Serial0/0, changed state to up

*Mar  1 00:01:32.659: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up

*Mar  1 00:01:57.271: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to down

r0(config-if)#

r0(config-if)#do sh ip int s0/0

Serial0/0 is up, line protocol is down

  Internet address is 172.16.1.1/24

  Broadcast address is 255.255.255.255

  Address determined by setup command

  MTU is 1500 bytes

  Helper address is not set

  Directed broadcast forwarding is disabled

  Outgoing access list is not set

  Inbound  access list is not set

  Proxy ARP is enabled

  Local Proxy ARP is disabled

  Security level is default

  <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Split horizon is enabled

  ICMP redirects are always sent

  ICMP unreachables are always sent

  ICMP mask replies are never sent

  IP fast switching is enabled

  IP fast switching on the same interface is enabled

  IP Flow switching is disabled

  IP CEF switching is enabled

  IP CEF Fast switching turbo vector

  IP multicast fast switching is enabled

  IP multicast distributed fast switching is disabled

  IP route-cache flags are Fast, CEF

  Router Discovery is disabled

  IP output packet accounting is disabled

  IP access violation accounting is disabled

  TCP/IP header compression is disabled

  RTP/IP header compression is disabled

  Policy routing is disabled

  Network address translation is disabled

  BGP Policy Mapping is disabled

  WCCP Redirect outbound is disabled

  WCCP Redirect inbound is disabled

  WCCP Redirect exclude is disabled

r0(config-if)#

*Mar  1 00:03:17.263: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up

r0(config-if)#do sh int s0/0

Serial0/0 is up, line protocol is up

  Hardware is GT96K Serial

  Internet address is 172.16.1.1/24

  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation HDLC, loopback not set//该接口的默认封装为HDLC 封装

  Keepalive set (10 sec)

  CRC checking enabled

  Last input 00:00:01, output 00:00:02, output hang never

  Last clearing of "show interface" counters 00:02:53

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: weighted fair

  Output queue: 0/1000/64/0 (size/max total/threshold/drops)

     Conversations  0/1/256 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 1158 kilobits/sec

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     7 packets input, 764 bytes, 0 no buffer

     Received 7 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     20 packets output, 1960 bytes, 0 underruns

     0 output errors, 0 collisions, 5 interface resets

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

         

r0(config-if)#

r0(config-if)#

r0(config-if)#

r0(config-if)#enc 

r0(config-if)#encapsulation ppp

r0(config-if)#

*Mar  1 00:04:33.727: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to down

r0(config-if)#

r0(config-if)#do ping 172.16.1.2

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)
由于R1还没有封装PPP，链路两端封装不同协议所以PING不通

 

r0(config-if)#

*Mar  1 00:05:39.947: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up

r0(config-if)#do ping 172.16.1.2

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/21/64 ms
链路的两端封装相同，则ping 测试应该正常

 

r0(config-if)#
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/21/64 ms

r0(config-if)#do sh int s0/0

Serial0/0 is up, line protocol is up

  Hardware is GT96K Serial

  Internet address is 172.16.1.1/24

  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation PPP, LCP Open//该接口的封装为PPP 封装

 

  Open: IPCP, CDPCP, loopback not set//网络层支持IP 和CDP 协议

 

  Keepalive set (10 sec)

  CRC checking enabled

  Last input 00:00:43, output 00:00:02, output hang never

  Last clearing of "show interface" counters 00:03:55

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: weighted fair

  Output queue: 0/1000/64/0 (size/max total/threshold/drops)

     Conversations  0/1/256 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 1158 kilobits/sec

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     58 packets input, 2928 bytes, 0 no buffer

     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     69 packets output, 3012 bytes, 0 underruns

         

r0(config-if)#

 

 

 
 
 
r1(config)#int s0/0

r1(config-if)#ip add 172.16.1.2 255.255.255.0

r1(config-if)#no sh

r1(config-if)#do sh

*Mar  1 00:03:00.043: %LINK-3-UPDOWN: Interface Serial0/0, changed state to up

r1(config-if)#do sh ip int

*Mar  1 00:03:01.047: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up

r1(config-if)#do sh ip int s0/0

Serial0/0 is up, line protocol is up

  Internet address is 172.16.1.2/24

  Broadcast address is 255.255.255.255

  Address determined by setup command

  MTU is 1500 bytes

  Helper address is not set

  Directed broadcast forwarding is disabled

  Outgoing access list is not set

  Inbound  access list is not set

  Proxy ARP is enabled

  Local Proxy ARP is disabled

  Security level is default

  Split horizon is enabled

  ICMP redirects are always sent

  ICMP unreachables are always sent

  ICMP mask replies are never sent

  IP fast switching is enabled

  IP fast switching on the same interface is enabled

  IP Flow switching is disabled

  IP CEF switching is enabled

  IP CEF Fast switching turbo vector

  IP multicast fast switching is enabled

  IP multicast distributed fast switching is disabled

  IP route-cache flags are Fast, CEF

  Router Discovery is disabled

  IP output packet accounting is disabled

  IP access violation accounting is disabled

  TCP/IP header compression is disabled

  RTP/IP header compression is disabled

  Policy routing is disabled

  Network address translation is disabled

  BGP Policy Mapping is disabled

  WCCP Redirect outbound is disabled

  WCCP Redirect inbound is disabled

  WCCP Redirect exclude is disabled

r1(config-if)#

r1(config-if)#

r1(config-if)#

*Mar  1 00:04:57.355: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to down

r1(config-if)#do sh int s0/0

Serial0/0 is up, line protocol is down

  Hardware is GT96K Serial

  Internet address is 172.16.1.2/24

  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation HDLC, loopback not set

  Keepalive set (10 sec)

  CRC checking enabled

  Last input 00:00:29, output 00:00:00, output hang never

  Last clearing of "show interface" counters 00:04:13

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: weighted fair

  Output queue: 0/1000/64/0 (size/max total/threshold/drops)

     Conversations  0/1/256 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 1158 kilobits/sec

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     35 packets input, 2518 bytes, 0 no buffer

     Received 35 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     18 packets output, 1316 bytes, 0 underruns

     0 output errors, 0 collisions, 3 interface resets

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

         

r1(config-if)#

r1(config-if)#

r1(config-if)#

r1(config-if)#en

r1(config-if)#encapsulation ppp

r1(config-if)#

*Mar  1 00:05:41.015: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up

r1(config-if)#