This Article Applies to:

 

All routers with mDNS Repeater function

 

Application Scenario:

 

 

Issue Description:

 

1. Devices are not discoverable across the subnet. In a home network environment, multiple VLAN interfaces are created for recreation, local servers, IoT and core devices. If the mDNS repeater is not working properly, the discovery between the devices in different VLAN interfaces would be affected. Devices are not able to see each other and establish communication.

2. AirPlay or Chromecast not working across VLAN. Especially, the TV is located in another VLAN interface while the phone or laptop stays in the core network interface. On the phone or laptop,

3. Printers are not found in the printer list. Some small office networks would set up wireless in another VLAN interface which is dedicated to laptops or divide employees' computers in a separate network for better management. While the printer is located in the core network, employees would not be able to print from the employee VLAN interface.

4. Some IoT or smart home devices cannot be controlled. Certain brands of IoT or smart home devices, require mDNS for discovery and control. If the mDNS repeater is not working properly, the smart hub or devices cannot be controlled by the phone. 

 

In conclusion, the issue would appear to be devices are not discoverable across VLAN interfaces.

 

Troubleshooting:

 

1. Make sure the Bonjour Service is correct.

 

If your service is already available in the preset we have created in Bonjour Service, you can skip to the next step.

 

You can search online for the service your device uses or Wireshark yourself to make sure the Bonjour Service is correct.

For example, launch the Wireshark and start to capture in the same LAN on any device. The filter is set to mdns, and you will see your correct service type. Double-check if you have set the correct Bonjour Service.

 

Bonjour Service are _googlecast._tcp.local and _airplay._tcp.local in this capture.

 

Bonjour Service format:

 

2. Make sure the mDNS Repeater is properly configured.

 

Please refer to the FAQ How to Configure mDNS on the Omada Controller or forum Knowledge Base Configuring mDNS Repeater

After configuring the Bonjour Service, you should examine your configuration. Specify the Service Network and Client Network. If you are going to cast your music or screen to a speaker or TV, you should set the VLAN interface of the speaker or TV as Service Network. Set the VLAN interface of the Phone as Client Network.

 

 

3. Check if you have set up any ACL entries.

 

ACL can block the mDNS. mDNS is using UDP 5353 to transmit the packet. If you have set up ACL, ACL can effectively stop the mDNS between the VLAN interfaces.

 

 

If you would like to make an inter-LAN ACL and expect the mDNS would work, based on what is mentioned above, the basic plan would be creating an IP-Group ACL to allow UDP 5353.

 

Note:

• Pay attention to the INDEX of your ACL. It affects the priority of your ACL. For more information about the ACL priority, please refer to the User Guide about ACL.
• If you want to further limit the Destination, you can use IP-Port Group instead to further restrict the Destination Port.

 

Deny entry:

 

Allow entry:

 

With the ACL scheme above, mDNS is still working. (Spotify mDNS was added to the mDNS service as it can send more packets than AirPlay.)

 

Note:

 

1. If mDNS is working properly, you should see the gateway forward the packet. mDNS packet is coming from the gateway IP 192.168.200.1. It means a successful forward by the gateway.

 

 

If there is no response to the mDNS, after a period of time, it will clear the cache.

 

2. When configuring ACL, if you have blocked access to the Destination = Gateway Management Page, this will stop mDNS from the Source network.

 

Update Log:

 

Jan 11th, 2024:

Update the format.

 

Recommended Threads:

 

List of Common mDNS(Bonjour) Service

 

Feedback:

 

• If this was helpful, welcome to give us Kudos by clicking the upward triangle below.
• If there is anything unclear in this solution post, please feel free to comment below.
• If you encounter such an issue, please follow the troubleshooting above to check your settings. Besides, ensure your Omada Controller and Gateway are running with the latest firmware.
• If the issue still exists after you try the suggestion above, please feel free to comment below or contact our support team with a detailed description of your issue and the steps you have tried.

 

Thank you in advance for your valuable feedback!

 

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