IPv6: Link Local Addresses

  • Assigned automatically as an IPv6 host comes online.
  • Similar to the 169.254.x.x addresses of IPv4
  • Always begins with “FE80” (First ten bits 1111 1110 10) followed by 54 bits of zeros.
  • Last 64 bits is the 48-bit MAC address with “FFFE” squeezed in the middle.
  • No subnet mask.
  • The multicast group for the Link Local address is always the least significant 1:FF and then 24 bits of LL address.

Example:

MAC Address: AABB.CC00.0200
Link Local Address becomes: FE80::A8BB:CCFF:FE00:200 which expanded out becomes:

FE80:0000:0000:A8BBl:CCFF:FE00:2000

  • 0xffee gets inserted between the two halves of the MAC address.
  • The seventh bit (universal/local flag) gets set to 1.

 

 

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