Multicast doesn't cross between IP _subnets_ - it doesn't necessarily have to do with VLANs, strictly speaking. But yes, in practice
VLAN←→subnet
Make sure IGMP is enabled. Devices join IGMP groups to announce they want to receive mDNS
- IGMP snooping
- IGMP proxying (if offered)
Depending on your router you might find helpful options like:
- mDNS reflector
- mDNS repeater
- any mDNS + description of multiple networks (Unifi)
tcpdump -i <interface> host 224.0.0.251 or port 5353 -A
Like others mentioned, Avahi is solid but the multicast reflection/repeater/relay must run on the device routing between the VLANS in question.
Disclaimer: Deployed and networked thousands of Chromecast at several hotel chains and their wildly variable enterprise networks. Wrote my own mDNS repeater-as-a-packet-rewriter to fine-tune TXT records.
- IGMP snooping
- IGMP proxying (if offered)
Depending on your router you might find helpful options like:
- mDNS reflector
- mDNS repeater
- any mDNS + description of multiple networks (Unifi)
Like others mentioned, Avahi is solid but the multicast reflection/repeater/relay must run on the device routing between the VLANS in question.Disclaimer: Deployed and networked thousands of Chromecast at several hotel chains and their wildly variable enterprise networks. Wrote my own mDNS repeater-as-a-packet-rewriter to fine-tune TXT records.