Using BBMD to communicate across multiple subnets - Facility Explorer - LIT-12012397 - Wireless Device - WNC: Wireless Network Coordinator/Gateway

WNC1800/FX-ZFR182x Pro Series Wireless Field Bus System Quick Reference Guide

Product name
WNC: Wireless Network Coordinator/Gateway
Document type
Reference Guide
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Revision date

If you have devices shown on the WNC Gateway but the FX Supervisory Controller does not discover them, they may be on another subnet. If devices are on another subnet, you may need to set up a BACnet Broadcast Management Device (BBMD) object in order to communicate with them.

A way to check this is to look at the IP addresses of the WNC Gateway and the Supervisory Controller you are trying to join. For example, the first three octets of the IP address should be the same. If they are not, then the devices are on different subnets and you need a BBMD object to properly route messages across the subnets.

Figure 1. BBMD network subnet

In the WNC Gateway UI, select the BBMD screen and set the Broadcast Disabled field to False. The Address-IP field should be set to the IP address of the Supervisory Controller, which contains the BBMD object. In the case of multiple controllers on the same network, only one will have the BBMD object. The Address Port field should be set to 47808.

  • BBMD setup is only required if the FX Supervisory Controller and WNC are on different IP subnets.
  • Changes to these parameters take effect immediately, but it can take up to 5 minutes before they are persisted in the WNC’s archive. If power is cycled before the archive occurs, the changes are lost.
  • If the network number is changed on the FX Supervisory Controller, the FX Supervisory Controller may need to be reset for it to take effect (after the network number is matched in the WNC).
Table 1. WNC BBMD descriptions
Symptom Identification Possible Cause Code
Broadcast Disabled Falso Setting the Broadcast Disabled to False enables the BBMD. The BBMD should not be enabled until the other val
Address IP Set to the IP Address of the associated FX Supervisory Controller.
Address-UDP Port 47808 This value must match the BACnet IP Port set in the Network Setup and typically does not change.
IP Broadcast Mask Do not change.

Each BBMD contains a list of the IP addresses of all the other BBMDs, including itself, in the network. All FX Supervisory Controller devices include BBMD capability and are automatically populated with other FX Supervisory Controllers in the system. However, the WNC Gateway needs to be manually added into FX Workbench.

Note: The WNC Gateway only allows one entry. This this limits peer-to-peer communications between FX-ZFR Pro devices to devices on the same subnet as the WNC Gateway or the subnet of the associated FX Supervisory Controller.

If there are multiple WNC Gateways on the same subnet, only one of them needs to be added (for example, only and not However, each WNC Gateway needs to be configured with the associated FX Supervisory Controller’s IP address of the device that holds the BBMD for the subnet that the associated supervisory controllers is a member of. In some cases, the subnet’s BBMD is on the associated FX Supervisory Controller, but not always.

Depending on how the Ethernet system is managed on a given site, it is not always apparent whether a BBMD is required by looking at the IP address of the device itself. If the Ethernet default gateway on the WNC and the Network LAN IP Router Address are different, then the BBMDs need to be configured.

If you are using Static IP (Auto DHCP = OFF), then an IT department assigns these addresses.