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Networks

Solved – Unifi USG DHCP Timeout/Failure

I’ve recently had an issue with one of the UniFi installations that I manage. The internet speed was upgraded so I made some optimizations to the network to better utilize the potential increase in bandwidth. Prior to completing my tweaks, all wireless clients suddenly could no longer get an IP address from the USG DHCP service, and consequently, could not connect to the internet. Various solutions exist online from rolling back the AP’s to an earlier firmware, to hard resetting everything. This issue only presented on the wireless – the wired connections worked as expected with DHCP. I really didn’t want to hamstring features and performance by rolling back firmware, or spending hours resetting and reconfiguring everything.

The final piece of the tweaks was to place the main and guest WiFi on VLANs. This entails creating a VLAN for each network in the “Networks” tab and then assigning each WiFi network to its corresponding VLAN.

The VLANs have a different DHCP subnet than the original configuration with the WiFi/DHCP issue, and once the VLAN and new DHCP subnet were provisioned to the USG, the devices on both wireless networks began pulling IP’s from their appropriate VLAN subnet and were able to get on the internet with no issues.

When we set up VLANs on the UniFi platform, routes are automatically created to allow the various subnets to communicate, so no functionality that existed prior to the 3 subnets was lost. Guest, wired, and WiFi are all cleanly segregated and all is running smoothly at this point.

As of 09/08/2020, all devices have current firmware. This includes access points, USG, and the controller on a fully patched, dedicated ubuntu server box. Three of the access points are on LTS. We have a Dream Machine on order to boost overall throughput potential.

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