Solved: Serials MAC address

alk1000 · ‎10-20-2005

Hi All,

Does anyone know why the serial ports don't have a MAC address?

Is it because they usually serve point-to-point links and therefore they use the system MAC address!

Cheers,

Daniel

frenzeus · ‎10-20-2005

MAC address is at the Layer 2. For example, Ethernet frame encapsulation includes a src & dst mac address for proper switching of packets to it's destination.

Serial, on the hand, can use different forms of Layer 2 encapsulation, HDLC, frame relay etc. Serial being a WAN interface, encapsulates packets that need to be sent out the serial interface with the appropriate Layer 2 encapsulation. If a serial interface is running frame relay, packets destined to be routed out of that interface will be encapsulated with frame relay header, with L2 info for appropriate switching by the Service Provider's FR switches.

A serial interface does not run Ethernet, therefore by it's nature, no MAC address.

HTH.

View solution in original post

frenzeus · ‎10-20-2005

MAC address is at the Layer 2. For example, Ethernet frame encapsulation includes a src & dst mac address for proper switching of packets to it's destination.

Serial, on the hand, can use different forms of Layer 2 encapsulation, HDLC, frame relay etc. Serial being a WAN interface, encapsulates packets that need to be sent out the serial interface with the appropriate Layer 2 encapsulation. If a serial interface is running frame relay, packets destined to be routed out of that interface will be encapsulated with frame relay header, with L2 info for appropriate switching by the Service Provider's FR switches.

A serial interface does not run Ethernet, therefore by it's nature, no MAC address.

HTH.

pccthailand · ‎10-25-2005

Hi

PPP and HDLC not use MAC-Address or IP Address to communication becoz it's point-to-point protocol or point-to-point link. For FR , it use DLCI that similar to Ethernet MAC-Address becoz it can apply to point-to-point or multipoint link