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Page 1: 1 IPv6 Address Representation. IPv6 Addressing2 Objectives IPv6 Addressing scheme IPv6 Address Plan IPv6 Address Types IPv6 Address with an Embedded IPv4

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IPv6 Address Representation

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IPv6 Addressing 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

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IPv6 Addressing 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

2001:0718:1c01:0016:020d:56ff:fe77:52a3 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.

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IPv6 Addressing 4

IPv6 Address Notation: Example

128.91.45.157.220.40.0.0.0.0.252.87.212.200.31.255

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IPv6 Addressing 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

FE80:0:0:0:2AA:FF:FE9A:4CA2 FE80::2AA:FF:FE9A:4CA2. multicast address

FF02:0:0:0:0:0:0:2 FF02::2 loopback address

0:0:0:0:0:0:0:1 ::1

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IPv6 Addressing 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 FF02:30:0:0:0:0:0:5 as FF02:3::5 correct representation = FF02:30::5

Leading zeroes in every group can be omitted. 2001:718:1c01:16:20d:56ff:fe77:52a3

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IPv6 Addressing 7

Rule 1- IPv6 Zero Suppression

To determine the number of 0 bits represented by the “::”1. count the number of blocks in the compressed address2. (-) subtract this number from 83. (*) multiply the result by 16.

For example1. FF02::22. two blocks - “FF02” block and “2” block. 3. 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 “::”.

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IPv6 Addressing 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, 21DA:D3::/48 and 21DA:D3:0:2F3B::/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.

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IPv6 Addressing 9

IPv6 Prefixes

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IPv6 Address Types

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IPv6 Addressing 11

IPv6 Addresses: Types and Scopes

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IPv6 Addressing 12

IPv6 Address Categories

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IPv6 Addressing 13

IPv6 Address Types

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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

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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)

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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 provider’s 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-bit’s 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 node’s interface identifier. This part of the IPv6 address, which represents the address’s low-order 64-

bit, is called the interface ID.

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Global Unicast Address: Example

2001:0410:0110::/48 is assigned by a provider

2001:0410:0110:0002::/64 network subnet within the organization

2001:0410:0110:0002:0200:CBCF:1234:4402 – node address within the subnet

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IPv6 Addressing 18

Global Unicast Address

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Global Unicast Address Allocation

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Global Unicast Address Allocation

Prefix (hex) Prefix (Binary) Description2000::/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

2400:0000::/19

2400:2000::/19

2400:4000::/21

0010 0100 0000 0000 IPv6 Internet

- APNIC

2600:0000::/22

2604:0000::/22

2608:0000::/22

260C:0000::/22

0010 0110 0000 0000

0010 0110 0000 0100

0010 0110 0000 1000

0010 0110 0000 1100

IPv6 Internet

-ARIN

2A00:0000::/21

2A01:0000::/23

0010 1010 0000 0000 0010 1010 0000 0001

IPv6 Internet

-RIPE NCC

3FFF::/16 0011 1111 1111 1110 6 Bone

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IPv6 Addressing 21

IPv6 Unicast Address Scopes

Three types of scopes:1. Link-local scope

Identifies all hosts within a single layer 2 domain. Called as link-local addresses

2. Unique-local scope Identifies all devices reachable within an administrative

site or domain typically contains multiple distinct links. Called as unique-local addresses (ULAs)

3. Global scope Identifies all devices reachable across the Internet. Called as global unicast addresses (GUAs)

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IPv6 Addressing 22

Local-Use Unicast Addresses

There are two types of local-use unicast addresses:

1. Link-local addresses used between on-link neighbors and for Neighbor

Discovery Processes.

2. Site-local addresses used between nodes communicating with other

nodes in the same site.

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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.

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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 address’s 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.

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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 router’s 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.

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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).

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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.

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Site-Local Address - Example For example, a site with ten subnets may assign site-local

prefixes such as the following: Subnet 1—FEC0:0:0:0001::/64 Subnet 2—FEC0:0:0:0002::/64 Subnet 3—FEC0:0:0:0003::/64 Subnet 4—FEC0:0:0:0004::/64 Subnet 5—FEC0:0:0:0005::/64 Subnet 6—FEC0:0:0:0006::/64 Subnet 7—FEC0:0:0:0007::/64 Subnet 8—FEC0:0:0:0008::/64 Subnet 9—FEC0:0:0:0009::/64 Subnet 10—FEC0:0:0:000A::/64

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Special IPv6 Addresses

The following are special IPv6 addresses: Unspecified address

unspecified address (0:0:0:0:0:0:0:0 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 (0:0:0:0:0:0:0:1 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.

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Multicast Addresses

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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.

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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:

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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.

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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.

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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.

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Format of the Multicast Address:Scope 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. 1 (interface-local scope)2. 2 (link-local scope) 3. 5 (site-local scope)

For example: Traffic with the multicast address of FF02::2 has a link-local

scope. An IPv6 router never forwards this traffic beyond the local link.

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Format of the Multicast Address:Scope Field

Example of Multicast Addresses with Different Scopes

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Format of the Multicast Address:Group 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.

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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.

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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.

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Solicited-Node Multicast Address RepresentationsConsists of the prefix FF02::1:FF00:0000/104 + 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 FF02::1:FF.

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Solicited-Node Multicast Address Representations

Examples of Solicited-Node Multicast Addresses Made from Unicast Addresses

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Anycast Address

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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.

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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.

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46

So, How many IPv6 addresses can a host

have?

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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:

1. A link-local address for each interface2. Unicast addresses for each interface (which could be a

site-local address and one or multiple global unicast addresses)

3. The loopback address (::1) for the loopback interface

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IPv6 Addresses for a Host

Typical IPv6 hosts are logically multihomed because they have at least two addresses with which they can receive packets

1. a link-local address for local link traffic 2. a routable site-local or global address.

Additionally, each host is listening for traffic on the following multicast addresses:

1. The interface-local scope all-nodes multicast address (FF01::1)2. The link-local scope all-nodes multicast address (FF02::1)3. The solicited-node address for each unicast address on each

interface4. The multicast addresses of joined groups on each interface

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And, How many IPv6 addresses can a host

have?

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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

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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

(FF01::1) The interface-local scope all-routers multicast address

(FF01::2) The link-local scope all-nodes multicast address (FF02::1) The link-local scope all-routers multicast address (FF02::2) The site-local scope all-routers multicast address (FF05::2) The solicited-node address for each unicast address on

each interface The multicast addresses of joined groups on each interface

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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.

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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 randomizeidentifiers=disabled command.

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EUI-64 address-based interface identifiers

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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.

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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.

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Converting 48-Bit MAC Addresses to IPv6 Modified EUI-64 Identifiers

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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).

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IPv6 Address with an Embedded IPv4 Address

Two kinds of IPv6 addresses have an embedded IPv4 address:

1. 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.

2. 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.

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IPv6 Address with an Embedded IPv4 Address

IPv4-compatible IPv6 address

IPv4-mapped IPv6 address

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IPv6 Address Representation for URL

colon (:) character is already defined to specify an optional port number for example: www.example.net:8080/index.html https://www.example.com:8443/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. [3ffe:b80:c18:1::50]:8080/index.html https://[2001:410:0:1:250:fcee:e450:33ab]:8443/abc.html

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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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