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如何处理 Cisco 交换机 err-disabled 故障?


2018-01-11 by dongnan

问题描述

一台 Cisco交换机,某端口莫名其妙自主关闭,服务器网卡物理指示灯灭状态,导致网络故障。

环境

  • 交换机型号 cisco WS-C3560X-24
  • 物理端口 interface g0/20,对应一台 XenServer 7.2 服务器,运行 10台 虚拟机。

排错步骤

端口状态

show interfaces g0/20

GigabitEthernet0/20 is down, line protocol is down (err-disabled)
  Hardware is Gigabit Ethernet, address is d8b1.90ce.xxx (bia d8b1.90ce.xxx)
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
  # ...省略
  Last input 5w0d, output 17:25:50, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 13405
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     2993272157 packets input, 1725425458885 bytes, 0 no buffer
     Received 7071063 broadcasts (4827224 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 4827224 multicast, 0 pause input
     0 input packets with dribble condition detected
     3077578710 packets output, 1187157223403 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     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 

如信息所示,端口关闭状态。 err-disabled 关键字引起了我的注意。

查找原因

通过搜索找到问题原因及解决方法,发现错误关闭状态是 loopback 导致的。

show interfaces status err-disabled

Port      Name               Status       Reason               Err-disabled Vlans
Gi0/20                       err-disabled loopback

不过这个网路结构并不复杂,亲自参与设计和实施,能够确定物理上不会有环路的问题,但是为什么会出现环路错误? 优先解决网络故障这个问题。

开启端口

errdisable recovery cause loopback

恢复状态,提示将在 182 秒后恢复端口

show errdisable recovery

ErrDisable Reason            Timer Status
-----------------            --------------
arp-inspection               Disabled
bpduguard                    Disabled
# ...省略
loopback                     Enabled
# ...省略
Timer interval: 300 seconds

Interfaces that will be enabled at the next timeout:

Interface       Errdisable reason       Time left(sec)
---------       -----------------       --------------
Gi0/20                  loopback          182

验证

端口状态

show int g0/20 status

Port      Name               Status       Vlan       Duplex  Speed Type
Gi0/20                       notconnect   150          auto   auto 10/100/1000BaseTX 

参考

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