BACnet/IP devices on different subnets are not discovered when doing a Discover on a Niagara G3 ENC controller.

Issue

There are BACnet/IP devices on several different IP subnets. Each subnet has one BACnet/IP device setup as a BBMD, however when doing a discover, no BACnet/IP devices from the different subnets are not being discovered.

Product Line

TAC I/A Series

Environment

Niagara G3, ENC-520

Cause

Setting up the BBMD in the ENC-520 is as simple as Changing its “Ip Device Property Type” from its default of “standard” to “Bbmd”. Once the ENC is configured as a BBMD device, then the BBMD’s required Broadcast Distribution Table (BDT) is automatically created. The ENC’s BDT includes its own IP address and Broadcast Distribution Mask (BDM), as well as the IP address and BDM of all other BBMD devices on the other IP subnets. The BDT allows for manual editing. We have found in some cases that the BDMs were being confused with the IP address subnet mask. The BDMs were being changed to reflect devices’ IP address subnet mask, which were something other that the standard BDM of 255.255.255.255. BBMD devices’ BDM must be set to 255.255.255.255.

Resolution

The Broadcast Distribution Mask must be set to “255.255.255.255” for each BACnet /IP Address listed in the ENC’s Broadcast Distribution Table. This is also true for other BACnet/IP devices configured as BBMDs on the other subnets.

1. Expand the ENC’s BACnetNetwork

2. Expand Bacnet Comm and then expand Network

3. Expand Ip Port and then expand Link

4. Expand the Broadcast Distribution Table

5. Expand any devices listed and set their Broadcast Distribution Mask to 255.255.255.255 for any one not listed as such. Save changes.

Try and discover again.