Roll your own MAC address?

This line was buried in the spec for a cheap Chinese serial server (RS-232/485 to Ethernet):

"The global only MAC address bought from IEEE, the user can define MAC address (please state when you make order)."

I thought ranges of MAC addresses were doled out to manufacturers by some entity, carefully managed so that no two were identical.

Now it's a roll your own MAC address?

Is this common in the cyberworld or is it just another fulfillment of my father's saying, "Son, there's nothing somebody can't make cheaper. Remember, you get what you pay for."

Dan

http://en.wikipedia.org/wiki/MAC_address


If you look at the actual MAC address specification, by changing bit 2 of the most significant byte, a MAC can be set as either global (0), where the org makes sure it is unique, or local (1), where you can do whatever you want.

Could be they have two versions, one with a fixed MAC and one with a variable one. I've never seen an application where changable MAC addresses was required or useful, except with wireless clients.

danw said:

a cheap Chinese serial server

Click to expand...

^^^THIS^^^ So I am going to go with an affirmation of what your dad said. I seems like the manufacturer apparently doesn't want to pay a fee for a global mac address.

This might not be as uncommon as you would think. Rockwell were recently shipping Powerflex 525's with duplicate MAC addresses. I also thought that this was not supposed to be possible.

I just bought two ip-camera's and when i'm looking up their info they have both very weird originating factories... based on their mac adresses... well it's running out like ipv4 i guess

Back in the dark ages when Ethernet was not as common as today I remember when we changed an expensive Siemens Communication card in a PC to a standard Ethernet Card we had to change the MAC adress of the new ethernet card in the PC since the communication card in the in the S5 PLC was set to only communicate with a certain MAC. Do not remember how.