8 Replies Latest reply: May 16, 2012 3:07 PM by Vivek Nagar RSS

    MAC address


      Hi, Friends...


      Recently, I have learned that when when One device send packet to another device, it automatically adds it MAC address. Ya got it!!!



      But, now my question is that this is limited with Ethernet Technology


      what about serial line...or leased line connectivity


      i want to know that what happend when packet goes through one serial interface to another serial interface. i know the fact that both addresses are necessary to succeessfully communication (MAC & IP Address).


      which addresses are used in serial technology plz  help me!!!!



        • 1. Re: MAC address

          On Serial Link we do not use Ethernet as you have already stated, instead the following are used:Frame Relay, ATM, PPP HDLC etc..


          Ethernet          MAC Addess

          Frame Relay   DLCI 

          ATM                VPI/VCI

          • 2. Re: MAC address
            Vivek Nagar

            Hello Mayur,


            For serial link, if you open the frame you can see mac address is

            broadcast MAC address (FF:FF:FF:FF:FF:FF).


            as serial P2P has only one end.





            • 3. Re: MAC address
              Kumar Mantri

              Hello Network specialist,


              there is no way it shows the broadcast address in the frame on serial links when using wan protocols hdlc,ppp, etc


              in L2 part if we use HDLC,PPP we can see just the type of wan protocol using and its contents thats all or if we use FRAMERELAY as a wan protocol and as we map with dlci's there dlci's act as a L2 address for framerelay network.



              • 4. Re: MAC address
                Mr. Akshay J

                Dear Mayur,

                On point to point links, just because there is only one way out, there is no need for any addressing.

                A simple example, when two people are talking to each other, they have no need to refer to each other by names, since only one person is listening to it on the other end.

                • 5. Re: MAC address

                  Thank you very much akshay!!!

                  • 6. Re: MAC address
                    Vivek Nagar

                    Hi Friend,


                    kindly see below line for HDLC


                    The Address field is used to specify the type of packet contained in the cHDLC frame; 0x0F for Unicast and 0x8F for Broadcast packets.




                    Address - In HDLC environments, the Address field is used to address the frame to the destination node. On a point-to-point link, the destination node does not need to be addressed. Therefore, for PPP, the Address field is set to 0xFF, the broadcast address. If both PPP peers agree to perform address and control field compression during LCP negotiation, the Address field is not included.




                    • 7. Re: MAC address
                      Kumar Mantri

                      Hi Vivek,


                      i absolutely agree with you that hexFF means all stations, but in the address of field of PPP protocol the address is of  hexFF which is of 1byte not the 48 bit mac-address FF:FF:FF:FF:FF:FF




                      • 8. Re: MAC address
                        Vivek Nagar



                        PPP address field set to 0xFF