How To Reconnect Ubiquiti WAPs Residing On Different Subnets After Controller Upgrade

Upgrading your Ubiquiti Controller is typically a simple task but one should use caution when performing an upgrade while the adopted Wireless Access Points (WAPs) are configured to reside on different subnets. If you applied Ubiquiti’s latest firmware upgrade and soon after discovered that your WAPs are unable to reconnect to the controller, there is a strong likelihood that your WAPs IP has reverted to it’s default address and is now unreachable. It’s worth noting that configuring your WAPs to reside within different subnets significantly increases both performance and security so reconsidering your network design to resolve this issue is not recommended. Fortunately, we have a simple solution that will help you get reconnected in no time.

Let’s begin by accessing the DHCP scope that’s responsible for assigning IP addresses to your WAPs subnet.

Steps: Open the “Server Manager” module and navigate to “Tools” and select “DHCP“.

Image of step 1

Review your current DHCP configuration and ensure that only the critical DHCP options are enabled. Typically, you’d want to keep options 003 (Router), 004 (Time Server), 006 (DNS Servers) and 015 (DNS Domain Name) enabled as they are deemed critical. Simply delete all remaining non-critical DHCP options from within the scope and reboot the impacted WAPs.

In our particular scenario, we had non-critical DHCP options 44, 46, 66 and 67 enabled. We simply removed those non-critical DHCP options and within a short time the WAPs began communicating with the Ubiquiti Controller again and our wireless connection was restored.

DHCP Scope Options

You can also set DHCP option 43 to point to the new controller if you are switching controllers.  This will make it so the WAP phones home to the new controller without having to manually reconfigure it.  Note that the value will need to be in hex so make sure to use a hex editor.  You will need to put 0104 in the beginning of the entry.  So if you want to convert it will be “0104C0A8030A” as the value without the quotes.


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