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Open mDNS service

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Hi guys,

Some months ago, I switched from using the hardware provided by my cable ISP to using my own cable modem (Technicolor TC4400-EU) combined with an XR700.

Since then, I am receiving warning e-mails from my ISP on a regular basis regarding security alerts since one of my devices is producing a security alert based on an open mDNS service.

I have not changed any devices at home or added new ones.

I also have not really changed my setup. I own a PS4 that is put into DMZ (had been put in DMZ before as well) which I would suspet to be the culprit but I am not sure.


The ISP has advised to block incoming connections on port 5353/UDP to adress the issue.

So three questions:

1. is there a way to find out which device is causing the issue?

2. is blocking the port 5353/UDP indeed the best solution for the issue?

3. if it is the best solution, how do I put this into the NetDuma OS?


Thanks for your help,



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I've never heard of this happening before, but I can tell you how to do what the ISP has suggested.

1. If you to to Settings > Advanced Settings > UPnP, you might be able to see the port in the list, and the IP address that's calling it.

2/3. I'm not sure whether blocking the port is the best solution, but it's certainly worth a go. Go to Settings > Content Filtering > Block Services, choose Always, press Add, set protocol to UDP, enter port 5353 in both fields, choose All IP Addresses, press Add.

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