The PDF linked to below discusses methods to use Bonjour across subnets.
Acronis Files Connect (formerly ExtremeZ-IP) supports advertising its file and print services using Bonjour. Bonjour is a protocol created by Apple for easy service discovery on a local area network. Although Bonjour is normally thought of as a multicast protocol there are methods that can be used to advertise Bonjour services across subnets.
The three ways to provide Bonjour service discovery across subnets or on a wide area network (WAN) are multicast routing, unicast DNS, or a Bonjour proxy for each service on every subnet. Each of these methods has advantages and disadvantages. In most situations, deciding factors will be the upfront effort required to setup the solution and the ongoing maintenance required to support the configuration. Further details can be found in the PDF linked to below.
- https://kb.acronis.com/sites/default/files/content/2013/01/39490/wanbonjour_1.pdf PDF/PPT Description: Using Bonjour Across Subnets