I just noticed that mac address of a serial port is not there in a 2911 router in PT. also while using eui-64 the serial picks up the mac of some a gigabit or fast ethernet interface.

  • MAC addresses are used by IEEE LAN protocols (ethernet, Wi-Fi, token ring, FDDI, etc.), and some of those use 48-bit MAC addresses, and some use 64-bit MAC addresses. Other protocols use something different (DLCI, VPI/VCI, etc.) or nothing at all.
    – Ron Maupin
    Commented Jan 5, 2019 at 18:39
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Commented Dec 14, 2019 at 18:18

2 Answers 2


Serial ports don't have or need MAC addresses. It's as simple as that.


MAC Addresses are specific to Ethernet interfaces - serial interfaces are point-to-point and use a different Layer 2 protocol (PPP, HDLC, FR etc.) for communication.

EUI-64 is most likely deriving it's address from another source on your router.

  • ... and to some other standards (some of which from the past) like Token Ring, FDDI, somewhat in Fibre Channel, ATM and others. Commented Jan 6, 2019 at 14:27

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