Why does multicast or mDNS fail across VLANs?
Discovery protocols are normally local-link. Crossing VLANs needs an intentionally configured reflector/gateway and security policy; simple routing may not be enough.
VLANs; mDNS/SSDP; reflector; ACL; IGMP.
Network engineering.
Show the technical detail
On a managed Wi-Fi plan
Treat as engineered network design, not consumer self-help.
On another provider's router
Most ISP hubs do not support advanced cross-VLAN discovery.
What to be careful of
Do not bridge safeguarding/business segments casually.
Where this comes from: Official · see the original source ↗ · Draft—technical review · checked 17 August 2026