AboutRalph Becker Expertise General networks, including LAN (ethernet, cable modem, DSL), dialup (modems), WAN (frame relay, ATM), and other related networking technologies.
Experience I have worked for 20 years in various network companies, in capacities including development, customer service, and operations. Check out my bio/ratings page!
http://www.allexperts.com/expert.cgi?m=1&catID=1049&expID=20679
Thanks for the reply, one more question remains and I would really appreciate your help.
I'm currently working on a project in which I have to program a number of PIC microcontrollers to send and receive data on an Ethernet LAN.
Now, In order to make this transition possible, each micro must somehow detect the MAC address of other micro units. For this, an ARP packet is sent, recieved on the other side and the rest of the story. In order to send the ARP, the sender should know it's own MAC address. How can we find the address?
Please correct me if I'm wrong on this point: the MAC address is already generated by the micro manufacturer and it has nothing to do with the unit's IP address.
Certainly and highly appreciated
Cheers
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Followup To
Question -
Dear Tejas
On the ethernet, when a packet needs to be sent, the MAC address of the host and destination is needed. The host can send an ARP to get the destination's MAC address, but the destination should some how generate the MAC address itself from it's IP address. Know that the first 3 bytes are generated by the manufacturer of the network card (and please correct me if I'm wrong), how are the next 3 bytes generated?
Shot
Answer -
Hi Sadegh, and thanks for your question
Each ethernet device is required to generate a unique mac address upon request. Most manufacturers use a small amount of firmware on the board and burn the unique address into the device at the factory.
You are correct about the first three bytes being assigned to the manufacturer. Here is a list of codes:
You are correct, each ethernet device must have its own internal MAC address. This is generates at a very low level, at Layer 2. It is independant of the IP address, as you suggest.
The IP address is generated at a higher level, at Layer 3. The IP software would always include a way to do an association between and IP address and its coresponding MAC address.
