Cisco nexus 7009 端口抖动延时调整

一、故障描述

   在运营商网络中，长距离的光缆需要经过OTN设备进行长发光传输到达对端设备。在使用的过程中，OTN设备为了保护链路传输会经常的进行端口倒换，如果该操作时间过长会导致N7K在该链路上流量降低到0，链路恢复后又开始缓慢的流量上升，对业务存在很大的隐患。

  光切换的时候设备接口控制器ethpm检测到状态异常会对接口进行shutdown操作然后等待重新协商，协商成功后端口正常UP，协商时间大概3-4秒。并且这在nexus设备上无法关闭，属于正常现象。以下是log信息，以E3/7为例：

VSnet-SW1-N7009 %ETH_PORT_CHANNEL-5-PORT_DOWN: port-channel7: Ethernet3/7 is down
VSnet-SW1-N7009 %ETHPORT-5-IF_BANDWIDTH_CHANGE: Interface port-channel7,bandwidth changed to 10000000 Kbit
VSnet-SW1-N7009 %ETHPORT-5-IF_DOWN_INITIALIZING: Interface Ethernet3/7 is down (Initializing)
VSnet-SW1-N7009 %ETHPORT-5-IF_DOWN_PORT_CHANNEL_MEMBERS_DOWN: Interface port-channel7 is down (No operational members)
VSnet-SW1-N7009 %ETH_PORT_CHANNEL-5-PORT_DOWN: port-channel7: Ethernet3/8 is down
VSnet-SW1-N7009 %ETH_PORT_CHANNEL-5-FOP_CHANGED: port-channel7: first operational port changed from Ethernet3/8 to none

二、端口抖动延时介绍

进过查询文档可以通过修改debounce timer来延迟端口down的时间，关于debounce timer的解释如下

The debounce timer delays notification of a link change, which can decrease traffic loss due to network reconfiguration. You can configure the debounce timer separately for each Ethernet port and specify the delay time in milliseconds. By default, this parameter is set for 100 milliseconds.

去抖动计时器延迟链路通知更改，这可以减少由于网络重新配置造成的流量损失。你可以为每个以太网端口单独配置去抖定时器并指定 以毫秒为单位的延迟时间。默认情况下，此参数设置为 100 毫秒。

三、配置如下

默认的时间是100ms，修改范围是0-5000ms，修改方法参考如下：

Configuring the Debounce Timer

You can enable the debounce timer for Ethernet ports by specifying a debounce time, in milliseconds (ms), or disable the timer by specifying a debounce time of 0.

You can show the debounce times for all of the Ethernet ports by using the show interface debounce

SUMMARY STEPS

1. configure terminal

2. interface ethernet slot/port

3. link debounce time milliseconds

4. show interface debounce

5. exit

6. copy running-config startup-config

DETAILED STEPS

 

	Command	Purpose
Step 1	configure terminal   Example: switch# configure terminal switch(config)#	Enters configuration mode.
Step 2	interface ethernet slot / port   Example: switch(config)# interface ethernet 3/1 switch(config-if)#	Specifies an interface to configure, and enters interface configuration mode.
Step 3	link debounce time milliseconds   Example: switch(config-if)# link debounce time 1000 switch(config-if)#	Enables the debounce timer for the amount of time (0 to 5000 ms) specified. Disables the debounce timer if you specify 0 milliseconds.
Step 4	show interface debounce   Example: switch(config)# show interface debounce switch(config-if)#	Shows the link debounce time for all of the Ethernet interfaces.
Step 5	exit   Example: switch(config-if)# exit switch(config)#	Exits the interface mode.
Step 6	copy running-config startup-config   Example: switch(config)# copy running-config startup-config	(Optional) Copies the running configuration to the startup configuration.

This example shows how to enable the debounce timer and set the debounce time to 1000 ms for the Ethernet port 3/1:

switch# configure terminal

switch(config)# interface ethernet 3/1

switch(config-if)# link debounce time 1000

switch(config-if)# 

This example shows how to disable the debounce timer for the Ethernet port 3/1:

switch# configure terminal

switch(config)# interface ethernet 3/1

switch(config-if)# link debounce time 0s

witch(config-if)#