Adiel's Notes

MAC address

EUI-48 structure
MAC address
(12 hex digits = 6 bytes = 48 bits)
XX:XX:XX:XX:XX:XX
XX:XX:XXXX:XX:XX
OUI
(Organizationally Unique Identifier)		NIC
(Device Identifier)
Byte 123456
b7b6b5b4b3b2U/LI/G

  • MAC address (medium access control address)

    • (other names: burned-in address, Ethernet hardware address, hardware address, and physical address)

  • EUI-48 (or MAC-48)

    • used in Ethernet, Wi-Fi, Bluetooth

  • EUI-64

  • unicast address:

  • broadcast address: FF:FF:FF:FF:FF:FF = all 1s

    • an adpaptor will pass all frames addressed to this address up to host

  • multicast address: the first bit is 1 but the address is not the broadcast address

    • an adpaptor can be configured to accept frames addressed to set of multicast addresses

  • Ethernet adaptor receives all frames, but accepts only:

    • frames addressed to its unicast address
    • frames addressed to the broadcast address
    • frames addressed to multicast addresses it is configured to accept
    • (all frames if in promiscuous mode)
Universal/local and individual/group bits in MAC addresses
U/L
I/G
Universally administeredLocally administered
Unicast (individual)X0-XX-XX-XX-XX-XX
X4-XX-XX-XX-XX-XX
X8-XX-XX-XX-XX-XX
XC-XX-XX-XX-XX-XX		X2-XX-XX-XX-XX-XX
X6-XX-XX-XX-XX-XX
XA-XX-XX-XX-XX-XX
XE-XX-XX-XX-XX-XX
Multicast (group)X1-XX-XX-XX-XX-XX
X5-XX-XX-XX-XX-XX
X9-XX-XX-XX-XX-XX
XD-XX-XX-XX-XX-XX		X3-XX-XX-XX-XX-XX
X7-XX-XX-XX-XX-XX
XB-XX-XX-XX-XX-XX
XF-XX-XX-XX-XX-XX
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