By default Sonos does not support speakers being on a VLAN that is different from the controller device. However, many put their speakers on an IoT VLAN to give separation for device.

The only catch [for now], is you have to use config.gateway.json (this file is on/needs to be created on the controller in the applicable site) to accomplish this (as of Controller 5.9.4).

If you need further information please see UniFi Advanced USG Configuration for help about where to create the config.gateway.json.

PLEASE NOTE:

• Prior to creating the .json file on your gateway, create the file in a text editor, such as Atom or Notepad++, and then validate your file at a JSON validator site such as https://jsonlint.com/.
• If the syntax fails verification, and you provision it on your gateway, it could cause reboot issues.
• If your unsure, reach out to the Ubiquiti Discord Chat or the UBNT Community Forums prior to saving/provisioning for support.

Below is an example of the config.gateway.json needed to allow IGMP Proxy support for Sonos speakers on a different VLAN from the controller.

{
	 "protocols": {
		 "igmp-proxy": {
			 "interface": {
				 "<VLAN interface where controller is eg. eth1.90>": {
					 "role": "upstream",
					 "threshold": "1"
				 },
				 "<VLAN interface where speakers are eg. eth1.60>": {
					 "role": "downstream",
					 "threshold": "1"
				 }
			 }
		 }
	 }
}