公司一个楼层交换机cisco2960的F0/21端口自己down了，一片怨声载道，人生鼎沸，妈了个B的。
通过命令：sh int f0/21 看到如下结果：
cisco12#sh int f0/21
FastEthernet0/21 is down, line protocol is down (err-disabled)
Hardware is Fast Ethernet, address is 0024.1351.2e95 (bia 0024.1351.2e95)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 uc,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not t
Keepalive t (10 c)
Auto-duplex, Auto-speed, media type is 10/100BaTX
input flow-control is off, output flow-control is unsupported
男性小说 ARP type: ARPA, ARP Timeout 04:00:00
Last input 19:29:25, output 19:29:20, output hang never
Last clearing of "show interface" counters never
新鲜人参怎么吃 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/c, 0 packets/c
5 minute output rate 0 bits/c, 0 packets/c
130997686 packets input, 111565127662 bytes, 0 no buffer
Received 3733082 broadcasts (0 multicasts)
0 runts, 0 giants, 0 throttles
38 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 3191174 multicast, 0 pau input
0 input packets with dribble condition detected
121355446 packets output, 78684231708 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface rets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out
通过红色部分了解端口处于故障状态，然后通过命令sh logging看看日志，结果如下：
cisco12#sh logging
炒南瓜丝Syslog logging: enabled (0 messages dropped, 1 messages rate-limited, 0 flushes, 0 overruns, xml disabled, filtering disabled)
Console logging: level debugging, 219 messages logged, xml disabled,
filtering disabled
Monitor logging: level debugging, 0 messages logged, xml disabled,
全世界最大的城市 filtering disabled
Buffer logging: level debugging, 219 messages logged, xml disabled,
filtering disabled
Exception Logging: size (4096 bytes)
Count and timestamp logging messages: disabled
File logging: disabled
Trap logging: level informational, 222 message lines logged
室内陈设
Log Buffer (4096 bytes):
hernet0/5, changed state to down
7w5d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to up
7w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to up
7w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down
曹操简介>萌是什么意思
7w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to up
7w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down
7w5d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to down
7w5d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to up
7w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to up
7w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down
7w5d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to down
7w6d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to up梦见两个小男孩
7w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to up
7w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down
7w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to up
7w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down
7w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to up
7w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down
7w6d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to down
7w6d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to up
7w6d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to up
8w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down
8w1d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to down
8w1d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to up
