How Should You Troubleshoot Cisco Wireless APs WLC Join Issues?
Before serving network users, it is essential to connect your Cisco Access Point (AP) to the Wireless LAN Controller (WLC) via the management interface. This connection enables the WLC to provide the necessary configuration information and firmware for the AP to operate.
Let’s understand the Wireless LAN Controller and its role in the operation of Wireless APs.
In a large organization where every floor has its own Access Point, moving from one floor to another can cause disruptions in your wireless connections. This is referred to as roaming. However, with the Wireless LAN Controller, disruptions can be minimized as it acts as a central manager for the Access Points.
It ensures stable connections by assuming the role of different Access Points. Therefore, the Wireless LAN Controller plays a crucial role in managing wireless network Access Points, which allows wireless devices to connect to the network seamlessly while preventing individual Access Points from working independently.
Cisco Wireless APs and WLC joining issues
Joining wireless APs and WLC is important for network stability and independent working. But, unfortunately, there are lots of joining issues that people fail to recognize. They either blame the WLC or APs for the same. As a result, they fail to enjoy the benefits of this combination.
Issues related to the registration of Wireless AP with WLC are common and can have various causes that can be identified using appropriate debugging commands. Some common factors that can lead to connection problems between WLC and Wireless APs include:
Presence of duplicate addresses on the network
If you get the error message “No More AP Manager IP Addresses Remain”, the problem is most likely the presence of IP addresses. This problem arises when one of the IP addresses on the network is identical to the AP manager’s IP address, causing the AP to reboot continuously without connecting to the controller.
Identical IP addresses are a frequent problem, and when debug commands are executed, they typically indicate that the discovery phase was successful, but no join request was sent by the AP. To solve this problem, you can either eliminate the device that has the duplicate IP address or modify its address.
Regulatory domain mismatch errors
To connect to the WLC, your AP needs to have the same regulatory domain. If they don’t match, a regulatory domain mismatch error occurs, which can be viewed in the message log when running the “debug capwap events” enable command.
To prevent this issue, it is suggested to choose APs that share the same regulatory domain as the WLC. Additionally, each regulatory domain that the WLC supports should be selected before connecting an AP through it. The output on the WLC message log will indicate this issue.
AP missing from the WLC AP Authorization List
If the AP is not listed in the WLC AP authorization list, an error can occur, which can be identified by using the “debug capwap events table” command on the WLC.
To resolve this issue, you need to add the access point to the authorization list by running the “config auth-list add mic <AP MAC Address>” command.
Corrupted certificates or keys on the AP
If you encounter an error with a certificate or public key corruption, it may cause the AP to not join the WLC. To check for corruption, run the “debug capwap errors enable” and “debug pm pki enable” commands and examine the results.
Sending not configured discovery message by AP from a VLAN on the controller
If the error message is “Received a Discovery Request with Subnet Broadcast with Wrong AP IP Address”, the problem is that a discovery message sent by AP from a VLAN is not configured on the controller. This means that the controller will drop the packets sent during the discovery phase.
Disabling of necessary ports on the firewall
To resolve this issue, make sure that the firewall has enabled the required ports for the AP to join the controller. These ports include UDP ports 5247 (for data) and 5246 (for control) for CAPWAP traffic, UDP ports 16666 and 16667 for mobility traffic, and TCP 161 and 162 for Simple Network Management Protocol (SNMP).
AP is configured as a mesh AP but being in bridge mode
If the error message is “AAA Authentication Failure for Username”, it means the AP is configured as a mesh AP but is currently in bridge mode. If the AP is missing from the WLC’s AP authorization list, you will need to add it to the list.
Once added, the AP will download an image from the controller and register in bridge mode. Following this, you can change the mode to local mode. Then, the AP will download the image, reboot, and register in local mode.
AP addresses being marked as a bad address by the DHCP server
During the Cisco Wireless APs registration process, access points can change their IP addresses frequently. As a result, DHCP servers on the network might consider the AP’s addresses as bad addresses due to frequent address renewal.
Now, you very well know the reasons behind Cisco wireless AP and WLC joining issues. So, consider these problems and troubleshoot them for seamless network connectivity.
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