For BACnet/e networks, crossing subnets is a more difficult prospect. Since BACnet/e uses BACnet Ethernet packets instead of IP packets, these packets cannot pass through typical IP-based network devices. Instead, BACnet routers must be installed on each segment that needs to talk to each other.
If there is not a router on both segments, the only option is to locate the E2H server so that it is on the same LAN segment or install and setup BACnet routers on each end. You could also purchase a gateway device that converts the BACnet/e to BACnet/IP.
Note: If the E2H server will be operating in the BACnet Ethernet mode, only 32-bit operating systems are currently supported.