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  1. Probably little mistake on last picture.
    On picture above is mac adress starting with CC0A and on the last picture is IPv6 address with CE0A.
    Anyway, thanks for great lesson.

  2. Hi Towdie,

    In reality the router does one more thing when creating the IPv6 address using EUI-64. The MAC address is chopped in two pieces but it will also “flip” the 7th bit. When it’s a 0 it will make it a 1 and the other way around. Here’s an example for the MAC address I used in this tutorial:


    Each hexadecimal character represents 4 binary bits:

    C = 1100
    C = 1100
    0 = 0000
    A = 1010

    Let’s put “CC” in binary behind each other:


    EUI-64 will flip the 7th bit of this address so it will become:


    Let’s calculate that back to hexadecimal:

    1100 = C
    1110 = E

    So the first part becomes CE0A. I’ll create a tutorial for this process and the reason behind it later on, but hopefully this explains the outcome of the address.

  3. Hi Jose,

    I’ve heard this one before but it doesn’t make much sense to me. This is from RFC 4291:

    2.5.3.  The Loopback Address
       The unicast address 0:0:0:0:0:0:0:1 is called the loopback address.
       It may be used by a node to send an IPv6 packet to itself.  It must
       not be assigned to any physical interface.  It is treated as having
       Link-Local scope, and may be thought of as the Link-Local unicast
       address of a virtual interface (typically called the "loopback
       interface") to an imaginary link that goes nowhere.
       The loopback address must not be used as the source address in IPv6
       packets that are sent outside of a single node.  An IPv6 packet with
       a destination address of loopback must never be sent outside of a
       single node and must never be forwarded by an IPv6 router.  A packet
       received on an interface with a destination address of loopback must
       be dropped.

    The only IPv6 addresses assigned on an interface are the global unicast and link-local address:

    R1(config)#interface GigabitEthernet 0/1
    R1(config-if)#ipv6 address 2001:DB8::1/64
    R1#show ipv6 interface GigabitEthernet 0/1
    GigabitEthernet0/1 is up, line protocol is up
      IPv6 is enabled, link-local address is FE80::F816:3EFF:FED4:B332 
      No Virtual link-local address(es):
      Global unicast address(es):
        2001:DB8::1, subnet is 2001:DB8::/64 
      Joined group address(es):

    So i’m not sure where it came from…


  4. Rene, just to be clear, they aren’t the same right?
    2001:41f0:4060:10::/64 and 2001:41f0:4060:A::/64 ?

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