CSIS 4823Data Communications

Networking – IPv6Mr. Mark Welton

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 SectionUnspecified 00...0 (128

bits)::/128 2.5.2

Loopback 00...1 (128 bits)

::1/128 2.5.3

Multicast 11111111 FF00::/8 2.7Link-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

IPv6 Address Types