1. CSIS 4823 Data Communications Networking – IPv6
Mr. Mark Welton

2. IPv6 Why IPv6? Ipv4 is a 32-bit addresses
This is 4,294,967,296 (4.2 x109) IP addresses
Large blocks are considered wither reserved or unroutable (i.e /8 private address space)
There are currently 7 billion people on the Earth
We could not even have every person get a device with a public IP under IPv4

3. IPv6 IPv6 established in 1998 by RFC 2460 Changes from IPv4
Security – extensions for authentication, data integrity, and confidentiality
Flow labels – classifying packets belonging to traffic flows
More options – more room for additional IP header options and extensions
Header format – reduced the required fields in the IP header
IP address space – 128 bits and “anycast” address, multicasts, and broadcast

4. IPv6 addressing IPv6 uses 128-bit addresses
This equates to x 1038 addresses
Roughly 295 IP addresses for every person on the Earth
Address scheme was designed to support efficient route aggregation
Subnets in IPv6 are suppose to contain 264 addresses
This would mean that the IPv4 space would consume 1/64th of the address space available in just one IPv6 subnet

5. IPv6 addressing
Addresses do not use dotted decimal notation, but rather hexadecimal
IPv6 address is commonly shown in four digit hexadecimal blocks
Each hexadecimal block is 16-bits
AAAA:BBBB:CCCC:0000:0000:11111:11111:1 111

6. IPv6 addressing
IPv6 shorthand allows for leading zeroes within a block can be eliminated
AAAA:BBBB:CCCC:0000:0000:11111:11111:1 111
So this address would become
AAAA:BBBB:CCCC:0:0:1111:11111:1111

7. IPv6 addressing
IPv6 shorthand also allows any consecutive number of zeros to be replaced by double colon so
AAAA:BBBB:CCCC:0:0:1111:11111:1111
would be shown as
AAAA:BBBB:CCCC::1111:1111:1111

8. IPv6 addressing the following three addresses are identical:
AA76:0000:0000:0000:0012:A322:FE33:2267
AA76:0:0:0:12:A322:FE33:2267
AA76::12:A322:FE33:2267

9. IPv6 addressing Why hexadecimal?
HEX: AA76:0000:0000:0000:0012:A322:FE33:2267
If we represent this IPv6 address in decimal it would have 12 more octets them a IPv4 address
DEC:

10. IPv6 addressing
IPv6 is not backwards compatible to IPv4 (you can not represent an IPv6 address in IPv4)
IPv4 addresses are compatible with IPv6 addresses
This is done by setting the first 80 bits to 0 and the next 16 bits to 1, with the final bits being the IPv4 address
the IPv4 address of would be:
0000:0000:0000:0000:0000:0000:ffff:
0:0:0:0:0:0:ffff:
::ffff:

11. IPv6 Subnet Masks
Masking IPv6 addresses is similar to IPv4 in that we use prefix lengths
To understand it first you must know the rules for IPv6 addressing

12. IPv6 Subnet Masks
The first 48 bits of IPv6 addresses are reserved for Internet routing (network address range)
ffff:ffff:ffff:0000:0000:0000:0000:0000
The 16 bits from bit number 49 to bit number 54 are for defining subnets (subnetting range)
0000:0000:0000:ffff:0000:0000:0000:0000
The last 64 bits are for device addresses
0000:0000:0000:0000:ffff:ffff:ffff:ffff

13. IPv6 Subnet Masks The most common subnet mask is and should be /64
The American Registry for Internet Numbers has the following guidelines for assigning IPv6 address space:
/64 – when it is known that only one subnet is needed
/56 – for small sites needing a few subnet within five years
/48 - for large sites
IETF (Internet Engineering Task Force) recommends all IPv6 networks be /64
IPv6 does not support NAT

14. IPv6 Address Types
Like IPv4, certain addresses are special and are identified by their high-order bits
These are defined in RFC 4291
Address type
Binary prefix
IPv6 notation
Section
Unspecified
(128 bits)
::/128
2.5.2
Loopback
(128 bits)
::1/128
2.5.3
Multicast
FF00::/8
2.7
Link-local unicast
FE80::/10
2.5.6
Global unicast
(everything else)

15. IPv6 Address Types
Note the /128 this is the IPv6 version of a /32 in IPv4
This specifies a host address (mask of all ones)
A /32 means a large aggregate Internet route in IPv6 not a host address

16. IPv6 Address Types Unspecified address
An unspecified address is an address of all zeros
Packets with an unspecified destination will be dropped by routers
The source address may be unspecified by devices that have yet to learn their address

17. IPv6 Address Types Loopback address
The loopback address in IPv6 is 0:0:0:0:0:0:0:1 or ::1/128
This is analogous to in IPv4

18. IPv6 Address Types Multicast
Multicast is a bit different in IPv6, though the basic principle is the same
The first thing you should notice is that there is no concept of a broadcast in IPv6
If you want to send a packet to all nodes, you should use the link-local all nodes multicast address of ff02::1

19. IPv6 Address Types Global unicast
Global unicast addresses are what you might call “normal” addresses, and will be assigned to interfaces on your devices

20. IPv6 Address Types Link-local unicast
Link-local unicast addresses are described in RFC (section 2.5.8) as follows:
Link-Local addresses are designed to be used for addressing on a single link for purposes such as automatic address configuration, neighbor discovery, or when no routers are present. Routers must not forward any packets with Link-Local source or destination addresses to other links.
So what does that all mean?

21. IPv6 Address Types Link-local unicast
It is the IPv6 equivalent of the x.x address space
In IPv6 this will be in the fe80::/10 network
How do we create a unique address?

22. IPv6 Address Types Link-local unicast
We use the routing prefix combine with the MAC address
How many bits are in a MAC address?
How many bit are in the device part of the address?
48 and 64

23. IPv6 Address Types Link-local unicast
We pad the 48 bit MAC address with ff:fe in the middle to create the Extended Unique Identifier 64 (EUI-64)
We must also flip the seventh bit in the first octet of the MAC address
This bit is the locally administered bit used to indicate that the OS has altered the address
48 and 64

24. IPv6 Address Types
48 and 64