Setting MSTP Network MAC id to non zero value creates b3 with unsupported Infinet id 0

Issue

After creating the MSTP network under the BACnet interface and changing the MAC address from its default of 0 (zero) to a different value, learning b3 devices and finding third party BACnet devices resulted in a very unstable MSTP network with issues such as devices going offline etc.

Product Line

SmartStruxure Solution

Environment

Automation Server - AS

Cause

The b3s are NOT designed to use MAC id zero even though it is a valid device ID per the BACnet protocol, in versions of SmartStruxure prior to 1.5 if the MAC address of the MSTP network was changed to something other than zero the learn process would assign MAC id 0 to one of the b3s in the network which in turn would cause the b3 not to communicate properly and could even bring down the MSTP network all together.

Resolution

In SmartStruxure versions prior to 1.5 DO NOT changed the MAC id of the MSTP network from its default of zero.

If the ID was changed and one of the b3s took id zero remove then proceed as follows...

  1. Power down the b3 with MAC id 0.
  2. Change the MAC id of the MSTP network in the AS back to zero.
  3. Warm start the AS
  4. Power up the b3 (make sure it is connected to the MSTP) on power up the b3 will detect that ID 0 is now in use and will clear its own id and stay off the network.
  5. Perform a b3 learn, the b3 should automatically be assigned an ID other than zero.