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Title: How do I check when low network speed and ping packet delay and loss? [Print this page]

Author: GTAC-Daisy Time: 2019-6-26 17:45
Title: How do I check when low network speed and ping packet delay and loss?
How do I check when low network speed and ping packet loss?

Author: GTAC-Daisy Time: 2019-6-28 10:09
Edited by Daisy at 2019-6-28 10:13

I. Symptom
The network speed is low, and ping packets are delayed or lost.

II. Possible causes
1. Abnormal wired environment
2. Wireless interference
3. High channel usage
4. Weak signal strength
5. Faulty STA NICs
6. Hardware faults or software version problems

III. Troubleshooting

1. Confirm the symptom to narrow down the fault scope.
Check whether ping packets are lost regularly and provide a snapshot about the fault.
(1) If packets are discarded regularly when the gateway is pinged, the STA gateway may have enabled flow control to limit the rate, or a security policy (for example, NFPP) is adopted.
(2) If packets are discarded irregularly when the gateway is pinged: Check whether ping packets between wireless STAs in the same network segment and under the same AP are lost. If not, check whether the wired network works properly. For example, check whether wired loops or attacks exist. If ping packets between wireless STAs are also delayed, the AP may be faulty or the wireless network works improperly.
(3) Check ARP entries learned at both ends and check whether ARP spoofing or address conflict exists.

2. Use a wired network to test wireless STAs in the same network segment and check whether packet loss or delay occurs.
If the wired network also works improperly, ask wired network engineers to check whether the switch has a loop or the network cable is faulty. If the wired network works properly, proceed with the following step.

3. Check wireless interference.
(1) Check whether co-channel or inter-channel interference exists. (Provide a snapshot about channel scanning.)
The MZB signal is used as an example. As shown in the preceding figure,channel 1 has five signals and the strength of two signals is greater than –75dBm, which indicates that the MZB signal has co-channel interference. (If thesignal strength is less than –75 dBm, interference can be ignored.) The MZBsignal also has inter-channel interference from signals in channel 3.

a1.png (508.99 KB, Downloads: 409)

Author: GTAC-Daisy Time: 2019-6-28 10:14
Edited by Daisy at 2019-6-28 10:17

Note: Multiple signals from the same radio card of an AP will be transmitted in the same channel but do not interfere with each other. As shown in the preceding figure, the three signals are in channel 1 but do not interfere with each other.
Signals from the same AP are the same but with different BSSIDs.

a2.png (134.65 KB, Downloads: 396)

Author: GTAC-Daisy Time: 2019-6-28 10:33
Channel interference will result in long delay, packet loss, association failure, or connection interruption and needs to be focused. If the fault is caused by channel interference, run the following commands: (You can also use the WIS for optimization.)
WS6008(config)#ap-config test
WS6008(config-ap)#channel 1 radio 1
//Radio 1 indicates 2.4 GHz, and channels 1, 6, and 11 do not interfere with each other.
WS6008(config-ap)#channel 149 radio 2
//Radio 2 indicates 5 GHz, and channels 149, 153, 157, 161, and 165 do not interfere with each other.

If Wi-Fi device interference cannot be avoided, perform optimization as follows:
If the frequency band is set to 40 Hz, change it to 20 Hz. Otherwise, channels 1 and 6 will have interference.
WS6008(config-ap)#chan-width 20 radio 1 ---Change the frequency band to 20 Hz.
If an AP has high power, decrease the power without affecting signal coverage, to reduce the overlapping area. In this case, interference does not exist even the channels are the same. In zero roaming scenarios, ensure that the power is higher than –65 dBm.
WS6008(config)#ap-config 123
WS6008(config-ap)#power local 50 radio 1
WS6008(config-ap)#power local 80 radio 2
Note: 2.4 GHz enables a low frequency, a large coverage area, and low power. 5 GHz enables a high frequency and a small coverage area. Ensure that the power of the 5 GHz band be maintained at a not too low level. Otherwise, coverage will be affected.
If 5 GHz does not have interference, you do not need to reduce the power.

Author: GTAC-Daisy Time: 2019-6-28 10:34
Edited by Daisy at 2019-6-28 10:36

(2) Check interference from non-WLAN devices.
Check whether devices such as microwave and microwave therapy exist in the surroundings.
Cordless phones or wireless cameras working in certain modes will occupy channels when they are placed within 3 m of WLAN devices. As a result, WLAN devices cannot be used.
Microwaves within 10 m of WLAN devices have high power and will occupy 50% of channels. As a result, the performance of WLAN devices in full load will be reduced by half.
Solution: Turn off interfering devices.
Check whether interference is from Wi-Fi devices or non-Wi-Fi devices. (Operations a and b both affect user experience. Perform them in off-peak hours.)
a. Enable spectrum scanning on an AP to check whether there is interference from non-Wi-Fi devices.
AP840-I(config)#spectral
AP840-I(config-spectral)#spectral enable
If logs are displayed, interference exists. You are advised to disable spectrum scanning 5 minutes after it is enabled because it affects user experience.

b. Switch the APto the listening mode and compare co-channels scanned by the AP to check theiranti-interference capabilities.
AP840-I(config)#wids

AP840-I(config-wids)#devicemode
AP840-I(config-wids)#device mode monitor

AP840-I(config-wids)#scan-channels802.11b channels 1

c. Check thebackground noise. If it is greater than –95 dBm, the wireless environment hasinterference. Check whether interference from non-Wi-Fi devices orinter-channel interference exists.
Ruijie#show dot wire 1/0

Note: Thebackground noise of –108 dBm has less interference than that of –95 dBm.

If there is nowireless interference, proceed with the following step.

Author: GTAC-Daisy Time: 2019-6-28 10:37
4. Check whether channel usage is high.
To check resource usage over the air interface, use either of the following methods:
Method 1: Run the shell command and then the athstats wifi 0 | grep count command in the CLI. Use the displayed values in the command output to divide each other. If the result is greater than 80%, resource usage over the air interface is high. If the result is greater than 88%, air interface resources are almost used up.
Method 2: Run the debug sdk link_qualityx command to check resource usage over the air interface. X indicates the radio ID. Run the sh log command to view the results.
Method 3: Run the show wis radio-link-quality command.
This command is supported only when the WIS function is enabled.
If the channel usage is high, configure rate limit and channel isolation and reduce co-channel interference. If the channel usage is normal, proceed with the following step.

Author: GTAC-Daisy Time: 2019-6-28 10:37
5. Check whether the signal strength is weak.
(1) The signal strength is weak, resulting in packet loss, or the access rate is low.
If there is no interference, check signals of wireless STAs and whether the negotiated rate is low. If the negotiated rate is too low, the whole network is affected because the wireless network works in half duplex mode. If more than 1/3 of wireless STAs have low rates, a problem occurs.
If the signal is weak, check whether the AP power is the highest and whether there are obstacles that result in weak signals. Adjust the AP location to resolve the problem.
(2) Packet loss is caused by low-rate STAs. Disable low-rate STAs as follows:
WS6008(config)#ac-controller
WS6008(config-ac)# 802.11b networkrate 1 disabled
WS6008(config-ac)# 802.11b networkrate 2 disabled
WS6008(config-ac)# 802.11b networkrate 5 disabled
WS6008(config-ac)# 802.11g networkrate 1 disabled
WS6008(config-ac)# 802.11g networkrate 2 disabled
WS6008(config-ac)# 802.11g networkrate 5 disabled
WS6008(config-ac)# 802.11a network rate 6 disabled
WS6008(config-ac)# 802.11a network rate 9 disabled
If there are only several low-rate STAs, directly disable them because they cannot be used and affect the overall performance. Typically, low-rate STAs have only one or two signal bars.

Author: GTAC-Daisy Time: 2019-6-28 10:38
If the signal strength is normal, proceed with the following step.
6. Check whether the STAs have faulty NICs.
Check whether all STAs encounter the fault. Replace them and perform a test. Check that the fault is caused by the environment or STA. Record the models and test results of other STAs. If tablets and mobile phones do not encounter the fault but PDAs do, perform the following test:
(1) Disable the energy-saving function for PDAs.
(2) If a PDA model is old, disable the 802.11n service for the AP.
(3) Upgrade the NIC drive. Typically, tablets or PCs are used.

Author: GTAC-Daisy Time: 2019-6-28 10:38
If all STAs are abnormal, proceed with the following step.
7.Check whether the hardware is faulty or the software version is abnormal.
Check whether the core AC and AP versions match and whether their versions are too earlier. You are advised to upgrade them to the latest versions at the official website.

Author: GTAC-Daisy Time: 2019-6-28 10:39
IV. Information collection
1.Collect information on the AC. show run
show ap-config running show log
show antenna all show ver detail show ap-c s
show ac-c c | include H.H.H //H.H.H indicates the faulty STA's MAC address.
show cpu
show memory

2.Collect information on the AP.
show run
show dot a a
show log
show dot wireless 1/0
show ver detail
show interface
show int dot11 1/0 (When packet loss occurs, run the command every 5s for three times.)
show int gi 0/1 (When packet loss occurs, run the command every 5s for three times.)
sh dot statistic 1/0 (When packet loss occurs, run the command every 5s for three times.)

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