Device: ER7212PC V2.20
Firmware before (working): 2.3.1 Build 20260117
Firmware after (broken): 2.4.2 Build 20260411
Controller: Omada 6.2.0.20
 

Issue:
After upgrading to firmware 2.4.2, mDNS proxy no longer relays service announcements between VLANs. Chromecast/Google TV is not discoverable from a different VLAN despite correct mDNS proxy configuration. Also some Home Assistant integrations failed.
 

Setup:

• TV (Google TV with Chromecast) on VLAN 30
• Casting device (phone) on VLAN 10
• mDNS rule "Media Sharing": serviceNetwork=VLAN30, clientNetwork=VLAN10, profile includes _googlecast._tcp.local
• Inter-VLAN routing works (ping from VLAN10 to VLAN30 succeeds)
• No ACL rules blocking VLAN10 → VLAN30

Troubleshooting done:

• IGMP Snooping enabled on both VLANs (Unknown Multicast = Forward, Flood Known Protocols = Enabled) → no change
• mDNS rule toggled off/on → no change
• Gateway rebooted multiple times → no change
• AdGuard (DNS filter) disabled → no change
• All wired devices disconnected (rogue DHCP ruled out) → no change
• Config backup from 2.3.1 era restored on 2.4.2 → still broken
• Casting works when phone and TV are on the same VLAN → confirms mDNS proxy is the issue
   

Troubleshooting left:

• Config backup from 2.3.1 era restored on downgraded firmware
   

Relevant changelog entry (2.4.2, item 30):
"Added support for transparent SSDP forwarding when both IGMP Snooping and unknown-multicast discard are active — Flood Known Protocols option in Multicast Snooping (requires Switch 6.2 firmware)"
 

As I understand, this chagne was added only for external managed switches? The ER7212PC built-in gateway has those "Unknown Multicast" or "Flood Known Protocols" options in the UI — but at the moment they are not functional, thus mDNS blocked?