Multicast DNS, or mDNS for short is used for a wide variety of applications, with the main ones being for Apple AirPlay, Chromecast, Matter and Apple HomeKit.

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What does mDNS do?

mDNS essentially allows devices that are on separate VLANs to talk to each other, such as iPhones, printers, Chromecast devices, smart home accessories and much more.

If you are using a UniFi UXG gateway, these devices can handle the mDNS traffic automatically, making inter-VLAN discovery for smart home devices super simple.

When using a dedicated IoT VLAN and HomeKit, mDNS is crucial for allowing device communication between VLANs from Apple Home Hub devices to the IoT accessories.

Multicast DNS is automatically enabled on brand new networks, but can be disabled as and when needed. Also, with recent versions of UniFi, the type of mDNS traffic can be now be specified to lock it down to HomeKit and Matter, for example.

How to enable mDNS in UniFi

To use UniFi mDNS, you need either a UniFi Gateway, such as the UXG Pro or a UniFi Cloud Gateway, such as the UDM Pro.

To enable mDNS, log into your UniFi Controller and click on Settings

Then, click on Networks

Then mDNS can be enabled, if not already

Specify which networks you want mDNS enabled on. For example, you wouldn't want mDNS enabled on networks that don't have supported devices.

How to enable mDNS Proxy in UniFi

With newer versions of UniFi, the types of traffic that is forwarded via mDNS can be specified, such as locking it down to just AirPlay.*

To specify the types of traffic, log into your UniFi Controller and click on Settings

Click on Networks

Under mDNS Proxy there are options for All, Auto or Custom

To select custom services, click on Custom, then Select Services

In the sidebar you can choose which services that mDNS will forward, such as Matter network, AirPlay and much more.