mdns floods with new macbook neos

Hi everyone,

We’ve identified a reproducible issue where new MacBook Neo models are effectively "shutting down" our dormitory internet. We have about 130 users on the network, and as soon as these specific devices connect, the network becomes saturated with traffic and crashes.

It isn't just one faulty unit—two different MacBook Neos have caused this so far. It seems like a massive mDNS/Bonjour flood. We suspect it might be related to how the device handles roaming between Access Points or a bug in its networking sleep/wake features.

Has anyone else experienced this with the Neo? If you found a specific setting (on the Mac or the router) to stop this, please let us know!

Hi korbinian81,

that sounds serious enough that I would treat it as a network incident first, not as a normal Mac setting issue.

I. Capture before changing too much

If possible, capture the traffic on the affected WLAN/VLAN and check whether the flood is really mDNS/Bonjour on UDP 5353, which Apple documents as Multicast DNS/Bonjour traffic.

Useful details would be:

• source MAC address of the affected Mac

• packet rate before and after sleep/wake

• behaviour during roaming between APs

• whether the traffic stops immediately when Wi-Fi is disabled on the Mac

II. Test one Mac in isolation

I would test one affected MacBook Neo on a separate SSID/VLAN with only one access point. If the issue only appears while roaming or after wake from sleep, that gives both Apple and the WLAN vendor a much clearer starting point.

III. Check WLAN multicast/mDNS handling

On the network side, check multicast filtering/rate limiting, Bonjour/mDNS gateway settings and whether mDNS is being bridged too widely across segments. Bonjour is normal on Apple devices, but it should not saturate a dormitory network.

IV. Escalate with diagnostics

Run Wireless Diagnostics on the Mac and keep the generated report. Together with a packet capture, this is the kind of evidence Apple Support or your WLAN vendor will need.

I would describe it carefully as: “specific MacBook Neo clients appear to trigger or generate excessive mDNS/Bonjour traffic in our WLAN under these conditions.” That avoids assuming a confirmed Apple bug before the capture proves it.

Just a gentle reminder — there is also a dedicated English Apple Support Community at discussions.apple.com. You are welcome to continue there if English is easier for you.

→ Security implications of Bonjour protocol for developers and administrators - Apple Support

→ TCP and UDP ports used by Apple software products - Apple Support

→ Apple SupportUse AirPlay with Apple devices - Apple Support

Thanks for posting your question in the Apple Support Communities. We have a Community for English speakers here: Official Apple Support Community

Please feel free to join and post your question there, or repost your question in German here: Offizielle Apple Support Community

Have a nice day!