MAC address best practice

How do you guys settle down on MAC addresses you use, for example with Ethernet Shields?

My Ethernet shields have always been using the MAC address from the following sources. Are those appropriate?

  • Ethernet MAC addresses from broken or disused computer motherboards and network cards that I have collected
  • MAC-like portions of SAS WWN of SATA or SAS hard drives and SAS RAID adapter cards that I personally own and is guaranteed never being used in iSCSI or FCoE setup

You can use DEAD BEEF FEED in most cases. The only caveat is no duplicate mac addresses on your private network.

All of my Ethernet shields came with a MAC address.

SurferTim:
You can use DEAD BEEF FEED in most cases. The only caveat is no duplicate mac addresses on your private network.

I have been using 00:00:D1:10:83:A8 a lot, the MAC-like portion from the SAS WWN of my own Adaptec 6805 SAS RAID controller. The said controller is living inside my storage server providing it a local RAID-5 array.

fcwilt:
All of my Ethernet shields came with a MAC address.

Clones don't usually come with MAC addresses. And especially mine as it is a W5500-based clone.

SurferTim:
You can use DEAD BEEF FEED in most cases. The only caveat is no duplicate mac addresses on your private network.

Same here, just change last 2 fields for a quick reference of my devices. Usually I start from 00 to 99.
Some thing like DEAD BEEF FE00 to DEAD BEEF FE99

As I know these MAC Adresses spaces are for private use. Same as 192.xxx.xxx.xxx and 10.xxx.xxx.xxx for IP.

x2:xx:xx:xx:xx:xx
x6:xx:xx:xx:xx:xx
xA:xx:xx:xx:xx:xx
xE:xx:xx:xx:xx:xx

Just like there are some free IP nets, like 192.168.x.x, there are free MACs. If the second least significant bit, the U/L (universal/local) bit, is set to one the MAC address is considered locally administered

I was used mac address for esp8266 to esp8266 communication with WiFiespnow.h library