topic Re: Reducing Multicast airtime in Wireless

Reducing Multicast airtime

Raphael_L — Thu, 11 Dec 2025 14:02:14 GMT

Hi ,

We have a fairly large Meraki setup. Approx 5500 APs scatered on 800 sites. Some sites are super small , and some have more than 40-50 APs.

This document seems to suggest that we should block mDNS to save some airtime.

We have 4 SSIDs. 2 of them are for Guests with L2 isolation , 1 for IOT and 1 for Corp ( no L2 isolation on both ).

We have 0 use case for mDNS on Corp.

For people that have medium to large campuses , what do you do about it ?

EDIT : IGMP snooping is enabled , Flood unknown multicast is disabled , Multicast to Unicast conversion is enabled.

aleabrahao — Thu, 11 Dec 2025 14:53:12 GMT

In my case, I usually do the following:

On the corporate network: I completely block mDNS.

On guest networks: With Layer 2 isolation, mDNS is irrelevant, so I block it anyway.

On the IoT network: I allow mDNS, but I use Bonjour Gateway and filter only the necessary services.

Consider enabling IGMP snooping and multicast-to-unicast conversion, when available.

Raphael_L — Thu, 11 Dec 2025 15:18:14 GMT

So you did create a L3 rule to block UDP 5353 on your corp ssid ?

And yes M2U is enabled and is enabled by default

RWelch-USA — Thu, 11 Dec 2025 15:53:19 GMT

Thanks for sharing the video (had not seen it before) but have seen BRKEWN-2046 slide deck before.

Good stuff.

aleabrahao — Thu, 11 Dec 2025 16:18:30 GMT

Yes, to be honest, our network is quite restricted, so we only allow what is necessary.

Philip D'Ath — Thu, 11 Dec 2025 19:53:27 GMT

That is a great video and provides a lot to think about.