Reducing Multicast airtime

[RaphaelL]

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. 

https://www.ciscolive.com/c/dam/r/ciscolive/apjc/docs/2025/pdf/BRKEWN-2046.pdf

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

This video is also a great one : https://www.youtube.com/watch?v=miRV8qDOKBE

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.

[alemabrahao]

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.

[RaphaelL]

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

[alemabrahao]

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

[RWelch]

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

Good stuff.

[PhilipDAth]

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