How to troubleshooting switch Layer 2 forwarding packet loss failure?

Created Oct 27, 2018 15:59:52Latest reply Dec 24, 2018 09:31:23 305 12 7 0
 Issue Description
How to troubleshooting Layer 2 forwarding packet loss failure?

there is packet loss when traffic 1.1.1.1 to 2.2.2.2 through switch, we need positioning what is the root cause.

version: S6720 V200R009C00SPC500

topo:

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transparent.gif Handling Process
1. configure traffic statistic on switch on inbound and outbound interface.
acl 3333
 rule permit icmp source 1.1.1.1 0 destination 2.2.2.2 0
traffic classifier test
 if-match acl 39999
traffic behavior test
 statistic enable
traffic policy test
 classifier test behavior test

#

interface GigabitEthernet 2/0/1

  traffic-policy test inbound

#

interface GigabitEthernet 2/0/2

  traffic-policy test outbound

#

2.Check the traffic statistics on the inbound and outbound interfaces to check whether packets are lost on the device. If the traffic statistics on the outbound interface are equal to the traffic statistics on the inbound interface, the device will lose packets. If the traffic statistics on the outbound interface is smaller than the traffic statistics on the inbound interface, the device loses packets.


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3.If it is confirmed that the device is lost, the Layer 2 forwarding only depends on VLAN+MAC. Therefore, you need to confirm the VLAN and MAC information of the device. Check whether the inbound and outbound ports of the traffic are in the same VLAN, and confirm that the destination MAC address of the traffic is correctly learned on the outbound interface (and also pay attention to whether there is a MAC address flapping on multiple ports).

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4.Check whether the status of the inbound and outbound ports, the rate, and the duplex mode are correct. The working modes of the ports of the two connected devices must be the same, and the link has no CRC error packet count.

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5.Check whether the discard count continues to increase in the outbound direction of the port. If yes, the interface has traffic congestion.

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6.if still cannot solve this issue, Please contact huawei engineer.
transparent.gif Root Cause

This is a example sharing about how to troubleshooting switch loss packets.

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Finn92  Novice   Created Oct 27, 2018 16:00:30 Helpful(0) Helpful(0)

I am very interested for this sharing , which is very helpful to our daily work. especially below

If it is confirmed that the device is lost, the Layer 2 forwarding only depends on VLAN+MAC. Therefore, you need to confirm the VLAN and MAC information of the device. Check whether the inbound and outbound ports of the traffic are in the same VLAN, and confirm that the destination MAC address of the traffic is correctly learned on the outbound interface (and also pay attention to whether there is a MAC address flapping on multiple ports).

This post was last edited by Finn92 at 2018-10-31 16:53.
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GongXiaochuan  Adept   Created Oct 27, 2018 16:00:48 Helpful(0) Helpful(0)

very good for sharing the steps for this case

This post was last edited by GongXiaochuan at 2018-10-30 14:52.
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Good Good Study Day Day Up
SupperRobin  Novice   Created Oct 27, 2018 16:02:33 Helpful(0) Helpful(0)

Modular QoS Command-Line Interface (MQC) simplifies the QoS configuration. On devices with traffic statistics implemented utilizing MQC, statistics are collected about packets that match traffic classification rules. The statistics on forwarded and discarded packets matching a traffic policy help you check whether the traffic policy is correctly applied and locate faults.

You can run the display traffic policy statistics command to view the statistics on forwarded and discarded packets matching a traffic policy only when MQC is used to implement traffic statistics. This post was last edited by SupperRobin at 2018-10-31 14:15.
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Skay  Adept   Created Oct 27, 2018 16:03:06 Helpful(0) Helpful(0)

Thanks for you sharing , for key information , we can make a repeat test .
If it is confirmed that the device is lost, the Layer 2 forwarding only depends on VLAN+MAC. Therefore, you need to confirm the VLAN and MAC information of the device. Check whether the inbound and outbound ports of the traffic are in the same VLAN, and confirm that the destination MAC address of the traffic is correctly learned on the outbound interface (and also pay attention to whether there is a MAC address flapping on multiple ports).
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No.9527  Mentor   Created Oct 27, 2018 16:06:47 Helpful(0) Helpful(0)

CPU usage is an important indicator to evaluate device performance. A high CPU usage will cause service faults, for example, BGP route flapping, frequent VRRP active/standby switchover, and even failed device login. You can use the display cpu-usage command to view CPU usage in real time and check whether the device is working properly.

This command displays information about the CPU usage on the MPU or the specified interface board. If the slave or slot slot-id is not specified, the CPU usage of the master MPU is displayed.

This post was last edited by No.9527 at 2018-10-31 11:47.
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Torrent     Created Oct 27, 2018 16:10:03 Helpful(0) Helpful(0)

At first, I want to thank you very much, it is a good example to all of us. we meet this issue in daily work but I do not know how to deal with.But can you share the whole configuration to us?
I am very interested for this post, which is very helpful to our daily troubleshooting. I always have similar problems in my daily work, but I do not know how to deal with them. Now I have a clear idea. Thank you very much for your sharing. Hope you can update continue like this
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faysalji  Novice   Created Oct 28, 2018 01:39:13 Helpful(0) Helpful(0)

Thanks for sharing troubleshooting case
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If you think my post/reply is useful, please click the Helpful button and flag my post as a BEST ANSWER. Thanks
faysalji  Novice   Created Oct 28, 2018 01:41:14 Helpful(0) Helpful(0)

These steps will be very helpful for routine work
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If you think my post/reply is useful, please click the Helpful button and flag my post as a BEST ANSWER. Thanks
Mysterious.color  Novice   Created Oct 28, 2018 12:54:06 Helpful(0) Helpful(0)

well explanation with images
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find what you love and let it kill you.
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