Hi, everyone! Today I’m going to introduce you to some common problems with Wireless Access.
2 Product FAQs
2.1 AP FAQs
2.1.1 How Do I View Operations on the Device?
Run the save logfile command to save the log information in the log file buffer to the log file.
To reduce the number of times information is written into the storage medium, information generated on the device is saved into the log buffer before being saved into the log file. When the log buffer is full, the system saves the logs in the log buffer to the log file.
You can run the save logfile command to save logs that are not automatically saved by system to the log file and clear the log file buffer.
Run the dir logfile/ command to check information about the log files saved on the storage medium.
Too many log files occupy device storage resources. The device stores a maximum of 200 log files by default. If the number of log files exceeds the maximum value, the system deletes the oldest log files.
Run the display logfile file-name command to check log files on the device.
NOTE: 2.1.2 How Do I Defend Against Bogus DHCP Servers at the User Side?
If a bogus DHCP server is deployed on a customer network, STAs may obtain invalid IP addresses from the bogus DHCP server but not from the AP or authorized DHCP server.
To defend against bogus DHCP servers, disable the DHCP trusted port on an AP in service set view (V200R005 and earlier versions) or VAP profile view (V200R006 and later versions). A DHCP server sends three types of DHCP packets: Offer, ACK, and NACK. When the AP receives any of these DHCP packets from a user-side interface, it considers the packet sender as a bogus DHCP server. The AP then discards the packets.
2.1.3 How Do I Locate VAP Creation Failure?
Operation procedure:
Check whether the VAP of the AP is fully configured.
Check whether the radio interface is bound to the radio profile.
Check whether the service set is configured correctly and bound to the radio interface.
2.1.4 Why Is a VAP Created?
VAPs are created to provide different services through different parameter settings, such as security policies, traffic scheduling, and virtual interfaces.
2.1.5 What States Does an AP Have?
normal: The AP is in normal state.
committing: The WLAN service configuration is being committed.
commit-failed: The WLAN service configuration fails to be committed.
2.1.6 What Are Characteristics of a Fat AP and a Fit AP? What Are Differences Between Them? What Is the Applicable Scenario?
| Item | FAT AP | FIT AP |
|---|---|---|
| Function | It integrates the WLAN physical layer functions, service data encryption, user authentication, QoS, network management, roaming technologies, and application layer functions. | A FIT AP has only the encryption and radio functions and cannot work independently of an AC. |
| Network solution | A FAT AP can provide wireless access independently.
| FIT APs must be work with an AC to provide wireless access.
|
| Management and maintenance | FAT APs have complex structure and are difficult to manage in a centralized manner. | Fit APs can go online with zero configuration. All configurations are performed on the AC, which facilitates centralized management of Fit APs and enables functions that are not supported by Fat APs, such as Layer 3 roaming and user-based rights delivery. |
| Application scenario | FAT AP applies to SOHO or small-scale WLANs. | FIT AP applies to large-scale enterprise WLANs, and industry and carrier WLANs. |
2.1.7 How Can I Determine Whether an AP Is Qualified?
Observe whether the AP indicator works normally. See description of indicators in installation guide of the packaging to determine whether AP indicators are working properly.
You can determine whether an AP is qualified by logging in to the AP. Before the login, ensure that the network cable used to connect to the AP is working properly.
NOTE: If the AP needs to connect to an Ethernet switch, ensure that the Ethernet cable is working properly. If the Ethernet cable is not working properly, for example, RJ-45 connectors are short-circuited, the AP may fail to be powered on or fail to work properly. Before connecting an Ethernet cable to the AP, use the cable test tool to check whether the cable is qualified. If the cable is unqualified, replace it.
The default IP address of the AP is 169.254.1.1.
Enter the default user name admin and initial password admin@huawei.com.
Assign the PC with an IP address on the same network segment as the default IP address of the AP. Connect the network cable to the AP and PC.
By default, the AP has Telnet enabled in V200R003 and STelnet enabled in V200R005 or later. Therefore, you can log in to the AP using Telnet in V200R003 and STelnet in V200R005 or later.
Connect the AP and PC using the serial cable.
Log in to the AP through the serial interface. On the AP serial interface, the baud rate is 9600 bit/s, the data bit is 8, the stop bit is 1, and there is no parity bit.
Check whether you can log in to the AP through the serial interface and enter the CLI.
If the login succeeds, the AP is working properly.
Check whether you can use a command to log in to the AP through the serial interface.
NOTE: If the login succeeds, the AP is working properly. If the login fails, reset the AP to restore the factory settings. Then, log in to the AP again.
NOTE: The default IP address of the AP is 169.254.1.1.
Enter the default user name admin and initial password admin@huawei.com.
2.1.8 Do APs Support Power Adjustment and What Is the Power Adjustment Mechanism?
Power adjustment is similar to channel adjustment.
2.1.9 Does an AP Configured with Multiple SSIDs Support the Same Number of Access Users as an AP Configured with One SSID?
Yes, an AP configured with multiple SSIDs support the same number of access users as an AP configured with one SSID.
2.1.10 Can an AP (Single Radio) with Different SSIDs Work at Different Channels?
An AP with different SSIDs cannot work at different channels. A radio has only one channel.
2.1.11 Is the Number of Access Users in Dual-band Mode Twice the Number of Access Users in Single-band Mode?
If there are sufficient system resources, the number of access users in dual-band mode is twice the number of access users in single-band mode. Limited by system resources, the number of access users in dual-band mode may not be twice the number of access users in single-band mode.
2.1.12 Can 802.11n Devices Work Only in 802.11n Mode? Can 802.11n Devices Work in 802.11bg Mode?
802.11n devices can work in multiple modes including 802.11bg mode.
2.1.13 What Methods Does an AP Use to Prevent Interference?
Adjusts channels.
Multiplexes channels.
Adjusts the rate at which packets are sent.
2.1.14 How Does an AP Adjust the Rate?
When signal quality becomes bad, an AP changes the modulation mode to reduce the transmission rate. This also reduces the bit error ratio.
2.1.15 Can Huawei 802.11n APs Automatically Switch Between 2.4 GHz and 5 GHz?
Huawei 802.11n APs cannot automatically switch between 2.4 GHz and 5 GHz frequency bands. Switching is performed manually.
2.1.16 Can Antennas in an Antenna Group on APs That Support MIMO Technology Be Used Independently?
Yes. When using independently, antennas using the MIMO technology cannot achieve the optimal performance. Multi-antenna MIMO technology can increase AP throughput and provide diversity receiving capability, improving the receive SNR.
2.1.17 What Is the AP Bandwidth When an AP Does Not Use the MIMO Antenna?
Theoretically, the 802.11n APs support at most 150 Mbps bandwidth when not using MIMO antennas.
2.1.18 What Are the Mappings Between WMM Queues and 802.1p Priorities?
WMM classifies data packets into four queues. 802.1P provides eight priorities. Users can configure the mappings between WMM queues and 802.1p priorities.
2.1.19 How Do I Calculate AP Power?
Assume the chip of the AP provides a transmit power of 50 mW, and the AP has two antennas, each of which can increase the transmit power by 2.5 times. The AP transmit power is 250 mW (50 x 2.5 x 2 = 250 mW), that is 24 dBm, which is calculated based on the formula: 10log (50 x 2.5 x 2)= 17 + 4 + 3 = 24 dBm.
2.1.20 Can AP Name, AP ID, and SSID Contain Chinese Characters?
The AP name and AP ID cannot contain Chinese characters. For V200R006 and later versions, the SSID can contain Chinese characters.
When the SSID contains Chinese characters, note the following:
NOTE: You can only use a command editor of the UTF-8 encoding format to edit Chinese characters.
SSIDs containing Chinese characters cannot be displayed on STAs that do not support the UTF-8 encoding format.
2.1.21 Why Is the RU Channel Usage 0 on the Central AP?
In the central AP+RU networking: Run the display radio { all | ap-group ap-group-name | ap-name ap-name | ap-id ap-id } command to check radio information about RUs. In the command output, CU (indicating the channel usage) is displayed as 0.
RUs do not proactively report the channel usage to the central AP. To query the channel usage of RUs, enable the data buffer function on the central AP.
The ap data-collection enable command enables the data buffer function on the central AP. After this command is executed, a large data buffer occupies the device memory and affects device performance. It is recommended that the undo ap data-collection enable command be executed to disable data buffer after the query.
2.1.22 What Roaming Types Are Supported by WLAN Devices?
The Fat AP and common cloud AP do not support roaming.
The Fat central AP and cloud central AP support intra-central AP roaming.
2.2 Antennas and Accessories
2.2.1 How Are Antennas Classified? Which Antennas Are Often Used by Huawei?
Usage: communication antennas, television antenna, radar antenna
Working frequency band: short wave antenna, ultra-short wave antenna, microwave antenna
Direction: omnidirectional antenna, directional antenna
Appearance: wire antenna, mesh antenna
Indoor antenna
Indoor directional antenna
Indoor SMA antenna
Outdoor antenna
2.4G&5G omnidirectional antenna
2.4G&5G directional antenna
Backhaul antenna
2.2.2 Can Antennas Amplify Signals?
Antennas are passive components. They can only collect wireless signals, but cannot amplify signals. A smaller antenna angle indicates a higher gain.
2.2.3 What Is Antenna Coverage?
The antenna coverage depends on the antenna angle and gain. The antenna coverage area is similar to a taper.
2.2.4 Is the Antenna Gain Determined During Production? Can the Antenna Gain Be Adjusted?
No, the gain is a fixed attribute of an antenna and cannot be adjusted.
2.2.5 What Are the Antenna Tilt, Field Angle, and Beam Angle?
Antenna tilt: angle between the antenna emission direction and the horizontal direction.
Field angle: angle between the two directions opposed to each other over the beam axis for which the luminous intensity is half that of the maximum luminous intensity.
The field angle often refers to the beam angle.
2.2.6 In Which Scenario Does the Outdoor AP Apply To?
The outdoor AP applies to squares, residential areas, schools, dormitories, campuses, open areas with dense population, commercial streets that have high requirements for wireless data services.
The following figure shows campus WLAN coverage scenario.
Any further questions, let us know!
