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## Forum Replies

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:

CC0A.180E.0000

Each hexadecimal character represents 4 binary bits:

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

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

11001100

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

11001110

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. If you want an example for EUI-64, I created a lesson that explains it in detail:

4. 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

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
address of a virtual interface (typically called the &quot;loopback
interface&quot;) 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
be dropped.
``````

``````R1(config)#interface GigabitEthernet 0/1
``````
``````R1#show ipv6 interface GigabitEthernet 0/1
GigabitEthernet0/1 is up, line protocol is up
2001:DB8::1, subnet is 2001:DB8::/64