clock rate 设置的是时钟频率 
 
R1#show int s0/0 
Serial0/0 is up, line protocol is down  
  Hardware is M4T 
  Internet address is 12.12.12.1/24 
  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,  
     reliability 255/255, txload 1/255, rxload 1/255 
  Encapsulation HDLC, crc 16, loopback not set 
  Keepalive set (10 sec) 
  Restart-Delay is 0 secs 
  Last input 00:00:04, output 00:00:04, output hang never 
  Last clearing of "show interface" counters never 
  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 
     4 packets input, 957 bytes, 0 no buffer 
     Received 4 broadcasts, 0 runts, 0 giants, 0 throttles 
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 
     7 packets output, 1019 bytes, 0 underruns 
     0 output errors, 0 collisions, 2 interface resets 
     0 output buffer failures, 0 output buffers swapped out 
     3 carrier transitions     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up 
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