IPv6 Address Representation

1
IPv6 Address Representation
2
Objectives

• IPv6 Addressing scheme
• IPv6 Address Plan
• IPv6 Address Types
• IPv6 Address with an Embedded IPv4 Address
• IPv6 Address Representation for URL
• IPv6 and Subnetting

3
IPv6 Addressing Rules

• 128 bits (or 16 bytes) long four times as long
  as its predecessor.
• 2128 about 340 billion billion billion billion
  different addresses
• Colon hexadecimal notation
• addresses are written using 32 hexadecimal
  digits.
• digits are arranged into 8 groups of four to
  improve the readability.
• Groups are separated by colons
• 200107181c010016020d56fffe7752a3
• Note
• DNS plays an important role in the IPv6 world
• (manual typing of IPv6 addresses is not an easy
  thing,
• Some zero suppression rules are allowed to
  lighten this task at least a little.

4
IPv6 Address Notation Example

• 128.91.45.157.220.40.0.0.0.0.252.87.212.200.31.255
  

5
Rule 1- IPv6 Zero Suppression

• Some types of addresses contain long sequences of
  zeros.
• To further simplify the representation of IPv6
  addresses, a contiguous sequence of 16-bit blocks
  set to 0 in the colon hexadecimal format can be
  compressed to , known as double-colon.
• For example
• link-local address
• FE800002AAFFFE9A4CA2 ? FE802AAFFFE9A4C
  A2.
• multicast address
• FF020000002 ? FF022
• loopback address
• 00000001 ? 1

6
Rule 1- IPv6 Zero Suppression

• Zero compression can only be used to compress a
  single contiguous series of 16-bit blocks
  expressed in colon hexadecimal notation.
• You cannot use zero compression to include part
  of a 16-bit block.
• For example,
• cannot express FF0230000005 as FF0235
• correct representation FF02305
• Leading zeroes in every group can be omitted.
• 20017181c011620d56fffe7752a3

7
Rule 1- IPv6 Zero Suppression

• To determine the number of 0 bits represented by
  the
• count the number of blocks in the compressed
  address
• (-) subtract this number from 8
• () multiply the result by 16.
• For example
• FF022
• two blocks - FF02 block and 2 block.
• The number of bits expressed by the is 96
  (96 (8 2)?16).
• Zero compression can only be used once in a given
  address.
• Otherwise, you could not determine the number of
  0 bits represented by each instance of .

8
IPv6 Prefixes

• The prefix is the part of the address that
  indicates the bits that have fixed values or are
  the bits of the subnet prefix.
• Prefixes for IPv6 subnets, routes, and address
  ranges are expressed in the same way as Classless
  Inter-Domain Routing (CIDR) notation for IPv4.
• An IPv6 prefix is written in address/prefix-length
  notation.
• For example, 21DAD3/48 and 21DAD302F3B/64
  are IPv6 address prefixes.
• Note IPv4 implementations commonly use a dotted
  decimal representation of the network prefix
  known as the subnet mask. A subnet mask is not
  used for IPv6. Only the prefix length notation is
  supported.

9
IPv6 Prefixes
10
IPv6 Address Types
11
IPv6 Addresses Types and Scopes
12
IPv6 Address Categories
13
IPv6 Address Types
14
Unicast IPv6 Addresses

• The following types of addresses are unicast IPv6
  addresses
• Global unicast addresses
• Link-local addresses
• Site-local addresses
• Unique local IPv6 unicast addresses
• Special addresses

15
Global Unicast Addresses

• Equivalent to public IPv4 addresses.
• Globally routable and reachable on the IPv6
  portion of the Internet.
• Unlike the current IPv4-based Internet, which is
  a mixture of both flat and hierarchical routing,
  the IPv6-based Internet has been designed from
  its foundation to support efficient, hierarchical
  addressing and routing.
• The scope, the portion of the IPv6 internetwork
  over which the address is unique, of a global
  unicast address is the entire IPv6 Internet.
• Global scoped communication are identified by
  high-level 3 bits set to 001 (2000/3)

16
Global Unicast Address

• Each aggregatable global unicast IPv6 address has
  three parts
• Fixed portion set to 001 The three high-order
  bits are set to 001. The address prefix for
  currently assigned global addresses is 2000/3.
• Global Routing Prefix Site Prefix
• Site prefix assigned to an organization (leaf
  site) by a provider should be at least a /48
  prefix 45 high-order bits (001).
• /48 prefix represents the high-order 48-bit of
  the network prefix.
• prefix assigned to the organization is part of
  the providers prefix.
• Subnet-id - Site
• With one /48 prefix allocated to an organization
  by a provider, it is possible for that
  organization to enable up to 65,535 subnets
  (assignment of 64-bits prefix to subnets).
• The organization can use bits 49 to 64 (16-bit)
  of the prefix received for subnetting.
• Interface-id Host
• The host part uses each nodes interface
  identifier.
• This part of the IPv6 address, which represents
  the addresss low-order 64-bit, is called the
  interface ID.

17
Global Unicast Address Example
200104100110/48 is assigned by a
provider 2001041001100002/64 network subnet
within the organization 20010410011000020200C
BCF12344402 node address within the subnet
18
Global Unicast Address
19
Global Unicast Address Allocation
20
Global Unicast Address Allocation
Prefix (hex) Prefix (Binary) Description
2000/16 0010 0000 0000 0000 Reserved
2001/16 0010 0000 0000 0001 IPv6 Internet -ARIN,APNIC,RIPE NCC,LACNIC
2002/16 0010 0000 0000 0 6 to 4 transition mechanisms
2003/16 0010 0000 0000 0011 IPv6 Internet - RIPE NCCC
24000000/19 24002000/19 24004000/21 0010 0100 0000 0000 IPv6 Internet - APNIC
26000000/22 26040000/22 26080000/22 260C0000/22 0010 0110 0000 0000 0010 0110 0000 0100 0010 0110 0000 1000 0010 0110 0000 1100 IPv6 Internet -ARIN
2A000000/21 2A010000/23 0010 1010 0000 0000 0010 1010 0000 0001 IPv6 Internet -RIPE NCC
3FFF/16 0011 1111 1111 1110 6 Bone
21
IPv6 Unicast Address Scopes

• Three types of scopes
• Link-local scope
• Identifies all hosts within a single layer 2
  domain.
• Called as link-local addresses
• Unique-local scope
• Identifies all devices reachable within an
  administrative site or domain typically contains
  multiple distinct links.
• Called as unique-local addresses (ULAs)
• Global scope
• Identifies all devices reachable across the
  Internet.
• Called as global unicast addresses (GUAs)

22
Local-Use Unicast Addresses

• There are two types of local-use unicast
  addresses
• Link-local addresses
• used between on-link neighbors and for Neighbor
  Discovery Processes.
• Site-local addresses
• used between nodes communicating with other nodes
  in the same site.

23
Link-local Unicast Address

• IPv6 link-local addresses are equivalent to IPv4
  link-local addresses defined in RFC 3927 that use
  the 169.254.0.0/16 prefix.
• IPv4 link-local addresses are known as Automatic
  Private IP Addressing (APIPA) addresses for
  computers running current Microsoft Windows
  operating systems.
• The scope of a link-local address is the local
  link.
• A link-local address is required for Neighbor
  Discovery (NDP) processes and is always
  automatically configured, even in the absence of
  all other unicast addresses.

24
Link-local Unicast Address

• Used only between nodes connected on the same
  local link.
• When an IPv6 stack is enabled on a node, one
  link-local address is automatically assigned to
  each interface of the node at boot time.
• IPv6 link-local prefix FE80/10 is used and the
  interface identifier in Extended Unique
  Identifier 64 (EUI-64) format is appended as the
  addresss low-order 64-bit.
• Bits 11 through 64 are set to 0 (54-bit).
• Link-local addresses are only for local-link
  scope and must never be routed between subnets
  within a site.

25
Link-local unicast address

• Because the low-order 64-bit of the link-local
  address is the interface identifier itself, the
  length of the link-local prefix is based on a
  64-bit length (/64).
• In IPv6, a node having an aggregatable global
  unicast address on a local link uses the
  link-local address of its default IPv6 router
  rather than the routers aggregatable global
  unicast address.
• If network renumbering must occur, meaning that
  the unicast aggregatable global prefix is changed
  to a new one, the default router can always be
  reached using the link-local address.
• Link-local addresses of nodes and routers do not
  change during network renumbering.

26
Site-Local Address

• Site-local addresses are equivalent to the IPv4
  private address space (10.0.0.0/8, 172.16.0.0/12,
  and 192.168.0.0/16).
• Private intranets that do not have a direct,
  routed connection to the IPv6 Internet can use
  site-local addresses without conflicting with
  global unicast addresses.
• Site-local addresses are not reachable from other
  sites, and routers must not forward site-local
  traffic outside the site.
• Site-local addresses can be used in addition to
  global unicast addresses.
• The scope of a site-local address is the site.
• A site is an organization network or portion of
  an organization's network that has a defined
  geographical location (such as an office, an
  office complex, or a campus).

27
Site-Local Address

• Unlike link-local addresses, site-local addresses
  are not automatically configured and must be
  assigned either through stateless or stateful
  address configuration processes.
• May be assigned to any nodes and routers within a
  site.

28
Site-Local Address - Example

• For example, a site with ten subnets may assign
  site-local prefixes such as the following
• Subnet 1FEC0000001/64
• Subnet 2FEC0000002/64
• Subnet 3FEC0000003/64
• Subnet 4FEC0000004/64
• Subnet 5FEC0000005/64
• Subnet 6FEC0000006/64
• Subnet 7FEC0000007/64
• Subnet 8FEC0000008/64
• Subnet 9FEC0000009/64
• Subnet 10FEC000000A/64

29
Special IPv6 Addresses

• The following are special IPv6 addresses
• Unspecified address
• unspecified address (00000000 or ) is
  only used to indicate the absence of an address.
• equivalent to the IPv4 unspecified address of
  0.0.0.0.
• used as a source address for packets attempting
  to verify the uniqueness of a tentative address.
• never assigned to an interface or used as a
  destination address.
• Loopback address
• The loopback address (00000001 or 1) is
  used to identify a loopback interface, enabling a
  node to send packets to itself.
• It is equivalent to the IPv4 loopback address of
  127.0.0.1.
• Packets addressed to the loopback address must
  never be sent on a link or forwarded by an IPv6
  router.

30
Multicast Addresses
31
Multicast Address Overview

• In IPv6, multicast traffic operates in the same
  way that it does in IPv4.
• Arbitrarily located IPv6 nodes can listen for
  multicast traffic on an arbitrary IPv6 multicast
  address.
• IPv6 nodes can listen to multiple multicast
  addresses at the same time.
• Nodes can join or leave a multicast group at any
  time.
• IPv6 multicast addresses have the first eight
  bits set to 1111 1111.
• An IPv6 address is easy to classify as multicast
  because it always begins with FF.
• Multicast addresses cannot be used as source
  addresses or as intermediate destinations in a
  Routing extension header.
• Beyond the first eight bits, multicast addresses
  include additional structure to identify their
  flags, scope, and multicast group.

32
Multicast Address

• Main goal of multicasting is having an efficient
  network to save bandwidth on links by optimizing
  the number of packets exchanged between nodes
• In IPv4
• 224.0.0.0/3, where the high-order 3-bit of the
  IPv4 address is set to 111
• In IPv6

33
Multicast Address

• IPv6 makes heavy use of multicast addresses in
  the mechanisms of the protocol such as
• The replacement of Address Resolution Protocol
  (ARP) in IPv4
• Prefix advertisement
• Duplicate Address Detection (DAD)
• Prefix renumbering.
• Format of the multicast address defines several
  scopes and types of addresses using the 4-bit
  fields Flag and Scope.
• These fields are located after the FF/8 prefix.
  
• The low-order 112-bit of the multicast address is
  the multicast group ID.

34
Format of the Multicast Address fields
High-order 3-bit of the Flag field is reserved
and must be initialized using 0 values. Remaining
bit indicates the type of multicast address.
35
Format of the Multicast Address Flags field

• Indicates flags set on the multicast address.
• The size 4 bits.
• The first low-order bit Transient (T) flag.
• T 0 ? T flag indicates that the multicast
  address is a permanently assigned (well-known)
  multicast address allocated by IANA.
• T 1 ? T flag indicates that the multicast
  address is a transient (non-permanently-assigned)
  multicast address.
• The second low-order bit Prefix (P) flag
• indicates whether the multicast address is based
  on a unicast address prefix.
• RFC 3306 describes the P flag.
• The third low-order bit Rendezvous Point
  Address (R) flag
• indicates whether the multicast address contains
  an embedded rendezvous point address.
• RFC 3956 describes the R flag.

36
Format of the Multicast AddressScope Field

• Indicates the scope of the IPv6 internetwork for
  which the multicast traffic is intended.
• The size 4 bits.
• In addition to information provided by multicast
  routing protocols, routers use the multicast
  scope to determine whether multicast traffic can
  be forwarded.
• The most prevalent values for the Scope field
  are
• 1 (interface-local scope)
• 2 (link-local scope)
• 5 (site-local scope)
• For example
• Traffic with the multicast address of FF022 has
  a link-local scope.
• An IPv6 router never forwards this traffic beyond
  the local link.

37
Format of the Multicast AddressScope Field
Example of Multicast Addresses with Different
Scopes
38
Format of the Multicast AddressGroup ID Field

• Identifies the multicast group and is unique
  within the scope.
• The size 112 bits.
• Permanently assigned group IDs are independent of
  the scope.
• Transient group IDs are only relevant to a
  specific scope.
• Multicast addresses from FF01 through FF0F
  are reserved, well-known addresses.

39
Multicast Assigned Address

• RFC 2373 defines and reserves several IPv6
  addresses within the multicast scope for the
  operation of the IPv6 protocol.
• These reserved addresses are called multicast
  assigned addresses.

40
Solicited-Node Multicast Address

• For each unicast and anycast address configured
  on an interface of a node or router, a
  corresponding solicited-node multicast address is
  automatically enabled.
• The solicited-node multicast address is scoped to
  the local link.
• Replacement of ARP in IPv4
• ARP is not used in IPv6, the solicited-node
  multicast address is used by nodes and routers to
  learn the link-layer addresses of neighbor nodes
  and routers on the same local link.
• As with ARP in IPv4, knowledge of link-layer
  addresses of neighbor nodes is mandatory to make
  link-layer frames to deliver IPv6 packets.
• Duplicate Address Detection (DAD)
• DAD is part of NDP.
• It allows a node to verify whether an IPv6
  address is already in use on its local link
  before using that address to configure its own
  IPv6 address with stateless autoconfiguration.
• The solicited-node multicast address is used to
  probe the local link in search of a specific
  unicast or anycast address already configured on
  another node.

41
Solicited-Node Multicast Address Representations
Consists of the prefix FF021FF000000/104
low-order 24-bit of the unicast or anycast
address. Low-order 24-bit of the unicast or
anycast address is appended to the prefix
FF021FF.
42
Solicited-Node Multicast Address Representations
Examples of Solicited-Node Multicast Addresses
Made from Unicast Addresses
43
Anycast Address
44
Anycast Address

• Anycast addresses can be considered a conceptual
  cross between unicast and multicast addressing.
• Unicast ? send to this one address
• Multicast ? send to every member of this group
• Anycast ? send to any one member of this group
• In choosing which member to send to, for
  efficiency reasons normally send to the closest
  one - closest in routing terms.
• So, anycast mean send to the closest member of
  this group.
• The network itself plays the key role in anycast
  by routing the packet to the nearest destination
  by measuring network distance.
• Anycast addresses use aggregatable global unicast
  addresses.
• They can also use site-local or link-local
  addresses.
• Note that it is impossible to distinguish an
  anycast address from a unicast address.

45
Reserved Anycast Address

• Also called the subnet-router anycast address.
• All IPv6 routers are required to support
  subnet-router anycast addresses for each of their
  subnet interfaces.
• Mobile IPv6 is an example of a protocol designed
  to use anycasting.

46
So, How many IPv6 addresses can a host have?
47
IPv6 Addresses for a Host

• An IPv4 host with a single network adapter
  typically has a single IPv4 address assigned to
  that adapter.
• An IPv6 host, however, usually has multiple IPv6
  addresses - even with a single interface.
• An IPv6 host is assigned the following unicast
  addresses
• A link-local address for each interface
• Unicast addresses for each interface (which could
  be a site-local address and one or multiple
  global unicast addresses)
• The loopback address (1) for the loopback
  interface

48
IPv6 Addresses for a Host

• Typical IPv6 hosts are logically multihomed
  because they have at least two addresses with
  which they can receive packets
• a link-local address for local link traffic
• a routable site-local or global address.
• Additionally, each host is listening for traffic
  on the following multicast addresses
• The interface-local scope all-nodes multicast
  address (FF011)
• The link-local scope all-nodes multicast address
  (FF021)
• The solicited-node address for each unicast
  address on each interface
• The multicast addresses of joined groups on each
  interface

49
And, How many IPv6 addresses can a host have?
50
IPv6 Addresses for a Router

• An IPv6 router is assigned the following unicast
  addresses
• A link-local address for each interface
• Unicast addresses for each interface (which could
  be a site-local address and one or multiple
  global unicast addresses)
• A Subnet-Router anycast address
• Additional anycast addresses (optional)
• The loopback address (1) for the loopback
  interface

51
IPv6 Addresses for a Router

• Additionally, each router is listening for
  traffic on the following multicast addresses
• The interface-local scope all-nodes multicast
  address (FF011)
• The interface-local scope all-routers multicast
  address (FF012)
• The link-local scope all-nodes multicast address
  (FF021)
• The link-local scope all-routers multicast
  address (FF022)
• The site-local scope all-routers multicast
  address (FF052)
• The solicited-node address for each unicast
  address on each interface
• The multicast addresses of joined groups on each
  interface

52
IPv6 Interface Identifiers

• The last 64 bits of an IPv6 address are the
  interface identifier that is unique to the 64-bit
  prefix of the IPv6 address.
• The following are the ways in which an IPv6
  interface identifier is determined
• A 64-bit interface identifier that is derived
  from the Extended Unique Identifier (EUI)-64
  address. The 64-bit EUI-64 address is defined by
  the Institute of Electrical and Electronic
  Engineers (IEEE). EUI-64 addresses are either
  assigned to a network adapter or derived from
  IEEE 802 addresses. This is the default behavior
  for IPv6 in Windows XP and Windows Server 2003.
• As defined in RFC 3041, it might have a
  temporarily assigned, randomly generated
  interface identifier to provide a level of
  anonymity when acting as a client.

53
IPv6 Interface Identifiers

• As defined in RFC 2472, an interface identifier
  can be based on link-layer addresses or serial
  numbers, or randomly generated when configuring a
  Point-to-Point Protocol (PPP) interface and an
  EUI-64 address is not available.
• It is assigned during manual address
  configuration.
• It is a permanent interface identifier that is
  randomly generated to mitigate address scans of
  unicast IPv6 addresses on a subnet. This is the
  default behavior for IPv6 in Windows Vista and
  Windows Server Longhorn. You can disable this
  behavior with the netsh interface ipv6 set global
  randomizeidentifiersdisabled command.

54
EUI-64 address-based interface identifiers
55
IPv6 Modified EUI-64 Format

• Stateless autoconfiguration is a mechanism that
  allows nodes on a network to configure their IPv6
  addresses themselves without any intermediary
  device, such as a DHCP server.
• The link-local address and stateless
  autoconfiguration are functions of IPv6 that
  automatically expand the Ethernet MAC address
  based on a 48-bit format into a 64-bit format
  (EUI-64).
• The conversion from 48-bit to 64-bit is a
  two-step operation.

56
The IPv6 Modified EUI-64 Format

• It is essential that all devices on the same
  network use the same mapping technique
• The most common type of layer 2 addresses are
  IEEE 802 MAC addresses.
• Layer 2 addresses 48 bits, arranged into two
  blocks of 24.
• Upper 24 bits organizationally unique
  identifier (OUI), with different values assigned
  to individual organizations
• Lower 24 bits device identifier
• EUI-64 Format
• It is similar to the 48-bit MAC format, except
  that while the OUI remains at 24 bits, the device
  identifier becomes 40 bits instead of 24.
• This provides gives each manufacturer 65,536
  times as many device addresses within its OUI.

57
Converting 48-Bit MAC Addresses to IPv6 Modified
EUI-64 Identifiers
58
IPv6 Address with an Embedded IPv4 Address

• IPv4-compatible IPv6 address is a special unicast
  IPv6 address used by transition mechanisms on
  hosts and routers to automatically create IPv4
  tunnels to deliver IPv6 packets over IPv4
  networks.
• Address is made up of six high-order fields of
  16-bit hexadecimal values, represented by X
  characters, followed by four low-order fields of
  8-bit decimal values (IPv4 address), represented
  by d characters (for a total of 32 bits).

59
IPv6 Address with an Embedded IPv4 Address

• Two kinds of IPv6 addresses have an embedded IPv4
  address
• IPv4-compatible IPv6 address
• Used to establish an automatic tunnel to carry
  IPv6 packets over IPv4 networks.
• related to a transition mechanism of the IPv6
  protocol.
• IPv4-mapped IPv6 address
• Used only on the local scope of nodes having both
  IPv4 and IPv6 stacks.
• Nodes use IPv4-mapped IPv6 addresses internally
  only.
• These addresses are never known outside the node
  itself and should not go on the wire as IPv6
  addresses.

60
IPv6 Address with an Embedded IPv4 Address

• IPv4-compatible IPv6 address

IPv4-mapped IPv6 address
61
IPv6 Address Representation for URL

• colon () character is already defined to specify
  an optional port number for example
• www.example.net8080/index.html
• https//www.example.com8443/abc.html
• In IPv6, the URL parser of Internet browsers must
  be able to differentiate between the colon of a
  port number and the colon in an IPv6 address.
• To identify the IPv6 address while still keeping
  the colon character for URL format (port number)
• the IPv6 address must be enclosed in brackets
• after the brackets, the port number may be added,
  followed by the directory and filename.
• 3ffeb80c181508080/index.html
• https//200141001250fceee45033ab8443/abc
  .html

62
IPv6 and Subnetting

• The only acceptable form to represent a network
  mask in IPv6 is CIDR notation.
• Although IPv6 addresses are in hexadecimal
  format, the network mask value is still a decimal
  value.

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