If it's unicast is all that's needs from VLAN 1 to VLAN 20, just use Layer 3 firewall rules on your firewall. Eg. - A rule to restrict VLAN 20 connecting to any other subnets or Internet locations. - A rule allowing VLAN 1 to communicate with VLAN 20. If you need multicast, as said above bonjour forwarding might achieve what you're looking for.
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