Why Is the GM Clock ID Different From My TSN enabled CompactDAQ Chassis's MAC Address?

Issue Details

• I am reading the GM Clock ID with a Property Node in LabVIEW to get the MAC address of the grandmaster. However, the returned value is my CompactDAQ's MAC address + 1. Why is this?
• I know that one of my TSN enabled CompactDAQ ethernet chassis's is used as a grandmaster in my network. When I read the MAC address of the grandmaster, it's different from the CompactDAQ's MAC address. Is this expected?

Solution

The cDAQ-9183/5/7/9 each have two MAC addresses. The MAC address visible from NI Measurement & Automation Explorer (MAX) is the chassis MAC address. There is another MAC address associated with the CompactDAQ chassis's internal ethernet switch, which is not visible from NI Measurement and Automation Explorer (MAX) because it's independent of the CompactDAQ's IP address.

The GM Clock ID returns the MAC address of the grandmaster in TSN. The property may be returning a different MAC address than expected because:

• It is using the MAC address of the CompactDAQ's ethernet switch.
  • You can verify if this is the case by checking the sticker on the back of the CompactDAQ. This displays is the ethernet switch MAC address.
• The CompactDAQ in question may not be the actual grandmaster.
  • The grandmaster is automatically selected through an election algorithm that compares clock quality, traceability, and priority. A more suitable clock may have been selected over the CompactDAQ.