Connecting Systems on Different Subnets

Quick question. Got a T3-LB on a customers network system. It’s a multiple IP/Subnet System with different sets of IP addresses. From an existing BMS thru windows in can ping the IP Address and it will ping back. In Niagara N4 I can manually set the IP address and port and get the device to come on-line. Then I can manually add my points sometimes even autodiscovery of the points works… However, the device does not show up in any system auto discovery whether Niagara N4 or JCI MSEA even T3000.exe from another connected laptop cannot see the address.

Any thoughts?

I think you’re saying that Niagara can discover the T3-LB and add points normally but in this multi/IP environment the controller cannot show up. Could be something related to the network ID, I have to confess our system doesn’t deal with them as smartly as it should. Chelsea will spend some time on this soon. Send on a simplified network diagram with IP and bacnet network ID settings and maybe we can spot something.


When you say that your system is a ‘multiple IP/Subnet System’, do you mean that BACnet devices are installed on different subnets? (different third octects in the address) It sounds like you’re describing a scenario where you might need to be using BBMDs to share the global BACnet commands like the ‘Whois’ and ‘Iam’ responses used during a discovery command. To be fully compliant, the devices should be responding to any Whois command that it sees on the trunk. You could put your PC on the same network subnet as your device and then run Wireshark to capture BACnet data to ensure that your device is seeing the request, and verify that it’s replying. I don’t have a T3-LB, so I’m not sure if it supports Foreign Device registration or not - that’s another functionality that allows it to respond to a remote device like an N4 station.

For sure we have not yet gotten to features like multiple subnets and foreign device registration. It’ll come eventually but we have a lot of urgent tasks on hand to clean up just now.