Jumbo frame tracking

Latest reply: Jan 26, 2020 17:48:55 75 3 3 1

Hello everyone,

Today I’m going to introduce you jumbo frame tracking.

In certain scenarios, the jumbo frame tracing method can be used properly to quickly locate the following difficult faults:

(1) The underlying entries of the gateway are incorrect. As a result, data forwarding is abnormal.

(2) The board is abnormal (for example, suspended), causing a data forwarding failure.

Let's look at the jumbo frame count first (Jumbo frame statistics are collected on physical interfaces).

Display interface 40GEx/x/x

http://image.hw3static.com/hi/staticimages/hi3msf/images/2017/0414/14/58f06b1c0936b.jpg

Jumbo Frame Definition

Jumbo: indicates the number of packets with length ranging from 1518 bytes to the maximum jumbo frame length (9216 bytes by default) and number of correct FCS packets.

Using Jumbo Frames to Locate Faults

Jumbo frames are easy to use. To use a jumbo frame, run the ping command with ignore-mtu and the packet size specified. Such as ping ignore-mtu –s 2000 –c 10 1.1.1.1. The preceding command is used to enable the CE switch to send 10 packets of 2000 bytes and ignore the MTU (similar to the setting of the DF bit).

The jumbo frame tracing method can be used to locate faults on the service plane and management plane of a data center. This method is simpler and faster than the flow statistics collection method. For example, how to locate the fault when access-1 and access-2 pass through five network devices? The roadmap is as follows:

(1) The access switch sends a specified number of Jumbo packets. Such as run the Ping ignore-mtu -s 2000 -m 100 -c 10 2.2.2.2 on access-1.

(2) Check whether the jumbo frame counts on the inbound and outbound interfaces are the same to locate the fault. For example, run the display inter 40GE1/0/1 | in Jumbo command on the ingress gateway to check whether the number of jumbo frames in the OUT direction is the same as the number of sent packets.

194846gvv4imbkx3bmg30i.png

If the bottom-layer entries of the gateway are abnormal, data forwarding becomes abnormal (for example, the bottom-layer chip is inconsistent with the control-plane entries). This type of fault often requires R&D personnel's help and takes a long time to locate. Jumbo frame tracing can quickly locate the fault point. If the entries on the control plane are correct but jumbo frames cannot be sent through the correct port, the gateway is faulty. In this case, you can use the following methods to quickly restore services:

(1) Reset ARP entries to synchronize entries between the gateway control plane and forwarding chip.

reset arp inter vlanif xx ip x.x.x.x

(2) VRRP master/backup switchover

Switch the standby device to the active state (enable preemption and increase the priority) so that the gateway is switched to the standby device.

(3) Entire system isolation

Isolate the active node and the standby node takes over data forwarding.

Why is the jumbo frame tracking method applicable only to the service plane and management plane? Why the storage plane and backup plane cannot be used? Are jumbo frames transmitted between servers?

Currently, jumbo frame transmission is enabled only between synchronization links of IP SAN servers.

Cause: The MPLS protocol is enabled on the storage plane and backup plane.

http://image.hw3static.com/hi/staticimages/hi3msf/images/2017/0414/14/58f06b1c0a6df.png

The MTU of the MPLS interface is 1500 bytes. When a packet is sent, the DMAC, SMAC, type field, and MPLS label (two layers) need to be encapsulated. The frame length exceeds 1518 bytes (that is, the minimum jumbo frame size). Therefore, the packets encapsulated by MPLS are counted as jumbo frames. Even if we ping 10 jumbo frames, the MPLS interface still has a large number of jumbo frames. Therefore, it cannot be determined that all the 10 jumbo frames are successfully forwarded. As a result, the abnormal node cannot be identified.

Is Jumbo Frame Tracking Unavailable for MPLS Interfaces?

In fact, the jumbo frame length can be adjusted by running commands. The method is as follows:

Set the maximum frame length allowed by 10GE1/0/1 to 9216 bytes (the default value is 9216 bytes) and the minimum frame length allowed by 10GE1/0/1 to 2000 bytes (the default value is 1518 bytes).

<HUAWEI> system-view

[~HUAWEI] interface 10ge 1/0/1

[~HUAWEI-10GE1/0/1] jumboframe enable 9216 2000

Note: V100R005C00 and earlier versions do not support the configuration of the minimum jumbo frame length.

After the jumbo frame size is adjusted on the MPLS interface, only the frames with more than 2000 bytes are counted as jumbo frames. In this case, the size of MPLS packets is not counted as jumbo frames. In the test, change the jumbo frame size to 2000, such as ping ignore-mtu –s 2000 –c 10 1.1.1.1.

After the preceding parameters are adjusted, the problem can be located by using the jumbo frame tracing method.

This is what I want to share with you today, thank you!


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lucian2003
Created Jan 21, 2020 16:14:39 Helpful(0) Helpful(0)

Thks to share
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Hello%20friends%2C%20I%20am%20a%20Telecommunications%20and%20electronics%20engineer%20and%20I%20just%20graduated%20as%20a%20master%20in%20telecommunications%20systems.%20I%20work%20in%20the%20telecommunications%20company%20of%20Cuba%2C%20ETECSA.%20I%20am%2035%20years%20old%20and%20I%20attend%20the%20transport%20network%20in%20my%20province%2C%20which%20is%20mainly%20Huawei.
PiotrekRGC
Created Jan 22, 2020 06:39:38 Helpful(0) Helpful(0)

Useful info, thanks
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NACA4412
Created Jan 26, 2020 17:48:55 Helpful(0) Helpful(0)

Thanks for sharing
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