What this means
The IEEE assigned the MA-L block 00203D to Honeywell Environmental & Combustion Controls. Every network interface they manufacture under this block has a MAC address beginning with these digits, followed by a unique per-device identifier. If a device on your network shows a MAC starting 00:20:3D, it is Honeywell Environmental & Combustion Controls hardware.
Frequently Asked Questions
Who owns MAC prefix 00203D?
00203D is registered to Honeywell Environmental & Combustion Controls in the IEEE MA-L registry.
What does the MA-L registry type mean?
An MA-L assignment, the IEEE's original OUI format, gives the vendor the first three octets and 16,777,216 device addresses under them. Honeywell Environmental & Combustion Controls's block covers 16,777,216 addresses.
What devices use 00203D?
Any network device with a MAC address starting 00:20:3D was manufactured by or for Honeywell Environmental & Combustion Controls.