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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. 10.0.0.0/8 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
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
IPv6
IPv6 uses 128-bit addresses This equates to 3.40292367 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
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:0000:0000:11111:11
111:1111
IPv6 addressing
IPv6 shorthand allows for leading zeroes within a block can be eliminated
AAAA:BBBB:CCCC:0000:0000:11111:11111:1111
So this address would become AAAA:BBBB:CCCC:0:0:1111:11111:1111
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
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
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:
170.118.0.0.0.0.0.0.0.18.163.34.254.51.34.103
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 10.20.30.40 would be: 0000:0000:0000:0000:0000:0000:ffff:10.20.30.40 0:0:0:0:0:0:ffff:10.20.30.40 ::ffff:10.20.30.40
IPv6 addressing
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
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
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
IPv6 Subnet Masks
Like IPv4, certain addresses are special and are identified by their high-order bits
These are defined in RFC 4291
IPv6 Address Types
Address type Binary prefix IPv6 notation Section
Unspecified 00...0 (128 bits)
::/128 2.5.2
Loopback 00...1 (128 bits)
::1/128 2.5.3
Multicast 11111111 FF00::/8 2.7
Link-local unicast
1111111010 FE80::/10 2.5.6
Global unicast
(everything else)
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
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
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 127.0.0.1 in IPv4
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
IPv6 Address Types
Global unicast Global unicast addresses are what you might call
“normal” addresses, and will be assigned to interfaces on your devices
IPv6 Address Types
Link-local unicast Link-local unicast addresses are described in RFC
2373 (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?
IPv6 Address Types
Link-local unicast It is the IPv6 equivalent of the 169.254.x.x
address space In IPv6 this will be in the fe80::/10 network How do we create a unique address?
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?
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
IPv6 Address Types