VyOS (1.2.x) provides a Multicast DNS repeater functionality.

Multicast DNS uses the 224.0.0.51 address, which is "administratively scoped" and does not leave the subnet. It re-broadcast mDNS packets from one interface to other interfaces. This enables support for e.g. Airplay devices across multiple VLANs.

set service mdns repeater interface eth0
set service mdns repeater interface eth1

Will re-broadcast all mDNS packets from eth0 to eth1 and vice versa.

mDNS repeater can be disabled using set service mdns repeater disable