Cat3550与UBR10K千兆互联,flow-control设置不一致导致的延时增大问题处理


一台Catalyst3550通过Gig0/2与一台UBR10012千兆互联,但是在运行中出现一个奇怪问题,就是在晚上流量高峰期,只要流量超过200M左右互联处就会产生600~800ms的延时,有时还有丢包,经检查发现千兆端口产生较多PAUSE output,show interface信息如下:
sh int gi0/2
GigabitEthernet0/2 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 000b.464e.3d00 (bia 000b.464e.3d00)
  Description: "connect to uBR10012 G3/0"
  Internet address is 10.0.3.38/30  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 51/255, rxload 16/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is
  input flow-control is off, output flow-control is on
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:42:44
  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 66028000 bits/sec, 29881 packets/sec
  5 minute output rate 202588000 bits/sec, 32768 packets/sec
     76350176 packets input, 118647447 bytes, 0 no buffer
     Received 40 broadcasts (0 IP multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 40 multicast, 0 pause input
     0 input packets with dribble condition detected
     83758909 packets output, 4029376771 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 1134732 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

通过Cisco网站分析可能是flow control工作不正常导致,其分析结果如下:
INFO: Switches use flow control to inhibit the transmission of packets to the  port for a specified period. Typically, if the receive buffer becomes full, the  port transmits a 'pause' packet that instructs remote ports to delay sending   more packets for a specified period. In addition, Gigabit Ethernet ports can  receive and act upon 'pause' packets from other devices.

通过查看3550的Gig0/2端口工作模式如下:
sh int transceiver properties | b Gi0/2
Name : Gi0/2
Administrative Speed: auto
Administrative Duplex: auto
Administrative Auto-MDIX: N/A
Administrative Power Inline: n/a
Operational Speed: 1000
Operational Duplex: full
Operational Auto-MDIX: N/A

通过查看端口信息,我们可以看出3550 Gig0/2 Flow control模式为: input flow-control is off, output flow-control is on , 另外一端UBR10K Gig3/0/0 Flow control模式为: output flow-control is XOFF, input flow-control is XOFF,从两端的工作模式来看Flowcontrol工作无效。
为了解决问题,在3550 Gig0/2端口配置flowcontrol send off强制关闭Flowcontrol,之后就工作正常了,再查看UBR10 Gig3/0/0 的Flow control模式变更为:output flow-control is XON, input flow-control is XON
Flow control 设置所产生的结果关系可以参考如下链接:
https://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/
release/12.2_25_sec/command/reference/cli1.html#wp1861670

posted on 2009-11-30 12:10 梯玛 阅读(2319) 评论(0)  编辑 收藏 引用 所属分类: 网络知识

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