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
