Introduction to IPv6

This topic is to discuss the following lesson:

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.

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.

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


Hello, Nice job at the introduction, I never new what anything past a trillion was called =). I’m sure i’ll have questions as I read through the following IPv6 lessons though.

Thanks again,


Thanks Chris! It’s difficult to imagine how large the IPv6 address space is :slight_smile:

If you have any questions, just let me know…

Hi Rene,

In the documentation is written “Every IPV6 interface contains at least one loopback address”.
Could you please explain the meaning of this sentence?
Maybe with an example…

Thanks for your support !

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…


Hi Rene,

If no NAT/PAT for IPV6. So we just to static route to outside interface. Is it correct ?

Best Regards,

Hi Chhayheng,

That’s right. On all your internal devices you can use public IPv6 addresses so there is no need for NAT anymore.


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

Hello Prateek,

That’s right. If you want to see it for yourself, try a conversion from hexadecimal to binary for “10” and “A”.