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UniFi AP Wireless Connection Problems and Troubleshooting Guide
Learn how to identify and troubleshoot common wireless connection problems in networks using UBNT UniFi Access Points. This guide covers signal quality issues, packet loss, incorrect IP configuration, DHCP problems, network loops, DTIM settings, AP placement, transmit power optimization, packet capture analysis, and hardware checks to help improve UniFi wireless network stability and performance.
Umut Can Yıldız
⸻
In some cases, even if your mobile devices or computers appear to have a healthy wireless connection and signal, you may experience situations where the content is not displayed at all or takes a very long time to load when trying to access the internet or any content on your local network.
In this article, you will find tips and ideas to identify the causes of connection problems that may occur or have already occurred in wireless network infrastructures where UBNT UniFi APs (UniFi Access Points) are used, and to resolve these problems.
Symptoms of a Problematic Connection
As mentioned in the introduction of our article, the most common problems seen in problematic wireless connections can be exemplified as follows: although the wireless signal quality appears to be good on the clients you use (mobile device, computer, etc.), the content is not displayed at all or takes a very long time to load when trying to access the internet or any content on your local network; frequent “page cannot be displayed” errors in your web browser; an exclamation mark appearing on the network icon of your computer despite having a connection; or, if there is a DHCP server on your network, the client you are using being unable to lease an IP address from the server.
The errors listed above may be caused not only by the general network structure but also by bugs in the UniFi software. Most of the software-related bugs that may cause these problems have been fixed in the latest UniFi software version. For this reason, before starting detailed troubleshooting, we recommend upgrading your system to the latest UniFi software.
Current Software Link for the UBNT UniFi Platform
Is the Problem on the Wired Network or the Wireless Network?
When investigating the source of the problem, the first step should be to start a continuous ping test from a computer connected wirelessly to your network, both to your default gateway and to an IP address or network address on the internet that you are sure is working properly, such as the Google DNS address 8.8.8.8, and observe packet losses simultaneously.
If packet loss occurs in both ping tests at the end of this process, the problem is only on your wireless network. If the ping to your default gateway is problem-free but packet loss occurs when pinging the 8.8.8.8 DNS address, you may be experiencing a problem with your internet connection.
! NOTE: Many laptop manufacturers automatically enable Wi-Fi power saving mode regardless of whether your computer is running on battery or normal power supply. If your computer is not dealing with a different workload during the ping test, ping packets may be transmitted with long intervals such as 1.25 seconds. This article focuses on solving disconnections and packet losses occurring in your wireless network rather than ping packet transmission intervals.
Check Your Configuration
There are three different errors in the sample IP configuration below. Could you notice them?
1- The subnet mask is too narrow to route connection requests to a gateway.
2- The entered gateway is not on the same subnet as the static IP address.
3- No DNS address has been assigned.
Incorrect static IP configuration on your UniFi APs may cause problems such as loss of communication between the APs and the controller, software update errors, time synchronization errors, and the disappearance of the wireless broadcast.
UniFi APs periodically check the gateway you enter during static IP configuration by pinging it. When the UniFi AP cannot reach the specified gateway for a certain period of time, it stops broadcasting wirelessly and switches to alert and scanning mode. In this mode, the status LED on the device blinks blue or green at certain intervals to indicate that there is no network communication, while also trying to find a nearby UniFi AP whose wireless broadcast it can repeat in order to fix the connection error.
! NOTE: In order for the automatic wireless repeating feature to work, the options Settings > Site > Enable Uplink Connectivity Monitor and Wireless Uplink, and Enable Automatic Uplink Failover must have been enabled beforehand.
To minimize problems that may arise from IP configurations, we recommend allowing UniFi APs to obtain IP addresses automatically from the network. If you do not have a structure that distributes IP addresses automatically, or if UniFi APs need to operate on a closed network, you can prevent wireless broadcast interruptions caused by static IP configuration by entering an IP address that is continuously accessible on your local network as the gateway when setting a static IP.
Proximity Between the Client and the AP
To determine whether the problem is caused by physical obstacles that disrupt coverage or incorrect positioning, move closer to the UniFi AP and check your connection efficiency. If the disconnections are resolved, you may need to re-plan your device placement or increase the number of devices to be used.
If the disconnections continue, there may be an issue related to the power supply of your device, such as long-distance PoE power delivery, poor cable quality, grounding problems, or interference caused by insufficient cable insulation quality, or there may be a hardware failure in the UniFi AP. We recommend removing the device from its location and checking whether the problem continues in a different area.
Network Loops
Network loop errors can be easily detected by using the terminal screen of the UniFi AP or UniFi Switch suspected of being problematic and the Wireshark software.
Connect to the UniFi AP on the switch where you suspect a network loop via PuTTY or the Terminal feature of the UniFi Controller, and enter the following code into the terminal screen for packet capture.
tcpdump -i br0 -n -v -s 0 -w /tmp/capture.pcap
The captured packets are saved as “capture.pcap” in the “/tmp” folder in the root directory of the UniFi AP you connected to via terminal. By using the “SCP” protocol of the “WinSCP” software, you can access the file system of the UniFi AP and transfer the created file to your computer.
! NOTE: When connecting to the UniFi AP via the SCP protocol, you can use the login credentials of the UniFi Controller software as the username and password.
Open the “capture.pcap” file that you transferred to your computer with the Wireshark software and check the traffic flow of Multicast/Broadcast packets. If the size of your Multicast/Broadcast packets appears to be around 100 kbps or lower, it means that there is no network loop problem in your system. If there is a loop problem in your network, you will see large amounts of multicast or broadcast traffic in the packet file you are viewing. To resolve the problem, you can disconnect the data connections of the devices connected to your network one by one until the Multicast/Broadcast traffic returns to normal levels, and identify the source of the problem.
Connection Scaling
The high output power provided by UniFi APs (TX Power) is excellent for networks that require a single AP, but it can be an incorrect choice in infrastructure applications where multiple APs will be installed. High output power is a suitable solution for expanding wireless coverage; however, high-power broadcasts also cause lower data transfer speeds.
In networks where multiple UniFi APs are installed, using all devices with high output power causes heavy frequency pollution, low connection speeds, and packet loss in data transfers.
High output power also prevents mobile devices that we use while moving from automatically roaming between APs. Mobile devices such as tablets and phones have a transmission power of 14 to 18 dBm. When mobile devices are used in hand, the hand may block the antenna on the mobile device and cause the transmission power of the mobile device to decrease to a certain extent. This situation causes disproportionate transmission scaling between the AP with high transmission power and the mobile device whose transmission power is reduced due to the way it is used, preventing the mobile device from leaving the AP it first connected to and connecting to another AP that is closer to it.
To avoid such problems, you need to adjust the transmission power of the devices by practically testing the quality of connectivity.
You can easily adjust the output power of UniFi APs through the “Group Configuration” feature on the UniFi Controller, or from the “Radio Cards” section in the Settings menu of the AP you want to modify.
Group Configuration Example
Disabling unnecessary features such as Band Steering, Minimum RSSI limit, Connection Monitoring, and Wireless Connection Balance may prevent incorrect diagnosis during troubleshooting of faults in your wireless network. For fast and accurate diagnosis, we recommend disabling such features during troubleshooting and running your UniFi APs in their most basic form.
DHCP Configuration
On some routers, DHCP servers that are incompletely or incorrectly configured transmit DHCP offer/response messages in Broadcast packet format, which causes excessive packet loss. The use of this technology in packet transmission causes slow connections and connection drops. To avoid problems, please make sure that your DHCP offers are transmitted in unicast packet format.
Changing the DTIM Interval
Some wireless receivers with old or faulty drivers may cause interruptions in broadcast/multicast packets and unusually slow connections when they cannot properly process DTIM Period 3. To resolve problems caused by this compatibility issue, you can find the DTIM interval suitable for your system by changing and testing the DTIM Periods from Settings > Wireless Networks > [click the edit button next to the broadcast name you use] > Advanced Options > 802.11 Rate and Beacon Controls > DTIM Periods.
DTIM Period Change Example
! NOTE: DTIM period changes negatively affect the battery consumption of mobile devices.
Monitoring Packets Passing Through the Network
In some cases, while there is no problem with the transmission of Multicast/Broadcast packets on your network, problems may occur with the transmission of Unicast packets. Tracking which packets on your network progress to which point will lead you to the source of the problem.
First, you need to determine through which “VAP” interface your computer is connected to the device you are connected to over the wireless network. For this process, connect via SSH to the UniFi AP to which you are connected wirelessly, using PuTTY or the Terminal feature of the UniFi Controller, and view all interfaces on the UniFi AP with the “iwconfig” command. You can determine whether the device you are connected to is the correct device and identify the “VAP” interface name based on the wireless frequency/wireless SSID or MAC address you are connected to.
In the example above, it is seen that we are using the “ath0” VAP interface on the UniFi AP AC EDU to which we are connected over the 2.4 GHz frequency. To check whether Broadcast packets reach the entire network through the UniFi AP, connect to the UniFi AP terminal screen via SSH and enter the code below. With this code, you can save the Broadcast packets arriving at the VAP interface you are connected to in a format that can be viewed with the Wireshark program.
Tcpdump -i athX -n -v -s 0 -w /tmp/broadcast.pcap
! NOTE: Replace the “athX” section in the code example above with the VAP interface name you identified in the previous step, and keep the Terminal screen open continuously after running the packet capture command.
From your computer connected wirelessly to the UniFi AP, ping the Broadcast IP address of your local network for a while, for example: ping 192.168.1.255 -t. Then stop both the ping and the packet capture process on the terminal screen of the UniFi AP. You can stop both processes with the Ctrl+C key combination.
In the previous steps, we saved the movement of Broadcast packets on the network to the “broadcast.pcap” file in the “/tmp” directory. Now, to check whether Unicast packets reach the entire network through the UniFi AP, connect again to the UniFi AP terminal screen via SSH and enter the code below. With this code, let us monitor the movement of Unicast packets passing through the VAP interface you are connected to on the network.
tcpdump -i athX -n -v -s 0 -w /tmp/unicast.pcap
From your computer connected wirelessly to the UniFi AP, ping the default gateway of your local network for a while, for example: ping 192.168.1.1 -t. Then stop both the ping and the packet capture process on the terminal screen of the UniFi AP. You can stop both processes with the Ctrl+C key combination. Then, connect to the UniFi AP using the “SCP” connection protocol of the “WinSCP” software and transfer the “broadcast.pcap” and “unicast.pcap” files created during the packet capture processes from the “/tmp” folder in the root directory of the AP to your computer.
! NOTE: When connecting to the UniFi AP via the SCP protocol, you can use the login credentials of the UniFi Controller software as the username and password.
You can open the “broadcast.pcap” and “unicast.pcap” files that you transferred to your computer with the Wireshark software and check at which stages packets are being lost, or you can share the captured files with us to get help regarding the issue you are experiencing.
Are the APs Restarting by Themselves?
Check the uptime of your UniFi APs from the “Devices” tab of the UniFi Controller. If you observe uptimes that coincide with connection interruptions and you could not obtain any results from the checks you performed based on the steps above, you may be encountering an undiscovered software bug. In this case, you can try resolving the problem with beta or previous stable software versions of the UniFi Controller and UniFi device firmware, or request help from our technical support team.
Check Your Hardware
Although it is a small possibility, you may be facing a problem related to the hardware of the UniFi AP. To test the wireless network hardware of the UniFi AP, first configure the wireless broadcast names of the suspected device or devices to be different from each other and from your general wireless network name. If the UniFi APs you use support 2.4 GHz and 5 GHz dual-band broadcasting, you should also configure the wireless broadcast names of your radio cards to be different from each other.
After changing the wireless broadcast names, connect to the terminal screen of the suspected UniFi AP via SSH and enter the code below.
iwpriv wifi0 get_txchainmask
The code above will show you the number of antenna connection points on the radio card of the UniFi AP. If the result is 3 or 5, it means your device has 2 antenna connection points; if the result is 7, it means your device has 3 antenna connection points; and if the result is 15, it means your device has 4 antenna connection points. If your UniFi AP broadcasts on both 2.4 GHz and 5 GHz (dual-band), first determine the antenna connection points of the 2.4 GHz radio card with the code above, and then determine the antenna connection points of the 5 GHz radio card with the command below.
iwpriv wifi1 get_txchainmask
If the antennas of a UniFi AP operating only on the 2.4 GHz frequency with a single radio card will be tested, follow the steps below to test the antenna connection points one by one.
In the example above, we identified the number of antenna connection points of the 2.4 GHz radio card on the device. The result “get_txchainmask:3” returned by the query shows that there are 3 antenna connection points on the 2.4 GHz radio card.
To test the antenna connection points of devices operating only on the 2.4 GHz frequency with a single radio card one by one, follow the steps below:
To perform data transfer only through antenna connection point number 1 of the UniFi AP:
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Umut Can Yıldız
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