Understanding IPv6 Slide: 1 Lesson 3 IPv6 Addressing

Understanding IPv6 Slide: 1

Lesson 3

IPv6 Addressing


Lesson Objectives

IPv6 address space IPv6 address syntax Unicast IPv6 addresses Multicast IPv6 addresses Anycast IPv6 addresses IPv6 interface identifiers IPv4 addresses and IPv6 equivalents


The IPv6 Address Space

128-bit address space 2128 possible addresses 340,282,366,920,938,463,463,374,607,431,768,211

,456 addresses (3.4 x 1038)

128 bits were chosen to allow multiple levels of hierarchy and flexibility in designing hierarchical addressing and routing

Typical unicast IPv6 address: 64 bits for subnet ID, 64 bits for interface ID


Current Allocation

Format Fraction of Allocation Prefix address space

Reserved 0000 0000 1/256

NSAP Allocation 0000 001 1/128

Aggregatable Global Unicast 001 1/8

Link-Local Unicast 1111 1110 10 1/1024

Site-Local Unicast 1111 1110 11 1/1024

Multicast 1111 1111 1/256


IPv6 Address Syntax

IPv6 address in binary form:0010000111011010000000001101001100000000000000000010111100111011

0000001010101010000000001111111111111110001010001001110001011010

Divided along 16-bit boundaries:0010000111011010 0000000011010011 0000000000000000 0010111100111011

0000001010101010 0000000011111111 1111111000101000 1001110001011010

Each 16-bit block is converted to hexadecimal and delimited with colons:21DA:00D3:0000:2F3B:02AA:00FF:FE28:9C5A

Suppress leading zeros within each 16-bit block:21DA:D3:0:2F3B:2AA:FF:FE28:9C5A


Compressing Zeros

Some IPv6 addresses contain long sequences of zeros

A single contiguous sequence of 16-bit blocks set to 0 can be compressed to “::” (double-colon)

Example: FE80:0:0:0:2AA:FF:FE9A:4CA2 becomes

FE80::2AA:FF:FE9A:4CA2 FF02:0:0:0:0:0:0:2 becomes FF02::2

Cannot use zero compression to include part of a 16-bit block FF02:30:0:0:0:0:0:5 does not become FF02:3::5.


IPv6 Prefixes

Prefix is the part of the address where the bits have fixed values or are the bits of a route or subnet identifier

IPv6 subnets or routes always uses address/prefix-length notation CIDR notation

Examples: 21DA:D3::/48 for a route 21DA:D3:0:2F3B::/64 for a subnet

No more dotted decimal subnet masks


Types of IPv6 Addresses

Unicast Address of a single interface One-to-one delivery to single interface

Multicast Address of a set of interfaces One-to-many delivery to all interfaces in the set

Anycast Address of a set of interfaces One-to-one-of-many delivery to a single

interface in the set that is closest

No more broadcast addresses


Unicast IPv6 Addresses

Aggregatable global unicast addresses

Link-local addresses Site-local addresses Special addresses Compatibility addresses NSAP addresses


Aggregatable Global Unicast Addresses

Top-Level Aggregation ID (TLA ID) Next-Level Aggregation ID (NLA ID) Site-Level Aggregation ID (SLA ID) Interface ID

TLA ID Interface ID

13 bits 64 bits

SLA ID

24 bits

001 NLA ID

16 bits

Res

8 bits


Topologies Within Global Addresses

Public Topology Site Topology Interface ID

TLA ID Interface ID

64 bits

SLA ID001 NLA ID

16 bits

Res

48 bits

Public Topology Site Topology Interface Identifier


Local-Use Unicast Addresses

Link-local addresses Used between on-link neighbors and for

Neighbor Discovery

Site-local addresses Used between nodes in the same site


Link-Local Addresses

Format Prefix 1111 1110 10 FE80::/64 prefix

Used for local link only Single subnet, no router Address autoconfiguration Neighbor Discovery

1111 1110 10 Interface ID

10 bits 64 bits

000 . . . 000

54 bits


Site-Local Addresses

Format Prefix 1111 1110 11 FEC0::/48 prefix for site

Used for local site only Replacement for IPv4 private addresses Intranets not connected to the Internet Routers do not forward site-local traffic outside

the site

1111 1110 11 Interface ID

10 bits 64 bits

000 . . . 000

38 bits

Subnet ID

16 bits


Special IPv6 Addresses

Unspecified address 0:0:0:0:0:0:0:0 or ::

Loopback address 0:0:0:0:0:0:0:1 or ::1


Compatibility Addresses

IPv4-compatible address 0:0:0:0:0:0:w.x.y.z or ::w.x.y.z

IPv4-mapped address 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z

6over4 address Interface ID of ::WWXX:YYZZ

6to4 address Prefix of 2002:WWXX:YYZZ::/48

ISATAP address Interface ID of ::0:5EFE:w.x.y.z


NSAP Addresses

0000001 NSAP-mapped address

7 bits 121 bits


Multicast IPv6 Addresses

Flags Scope Defined multicast addresses

All-Nodes addresses FF01::1 (Node Local), FF02::1 (Link Local)

All-Routers addresses FF01::2 (Node Local), FF02::2 (Link Local), FF05::2 (Site

Local)

1111 1111 Group ID

8 bits 112 bits

Flags

4 bits

Scope

4 bits


Recommended Multicast IPv6 Addresses

Only 32 bits are used to indicate the Group ID Single IPv6 multicast address maps to a single

Ethernet multicast MAC address

1111 1111 Group ID

8 bits 32 bits

Flags

4 bits

Scope

4 bits 80 bits

000 … 000


Solicited-Node Address

Example: For FE80::2AA:FF:FE28:9C5A, the corresponding

solicited-node address is FF02::1:FF28:9C5A

Acts as a pseudo-unicast address for very efficient address resolution

Interface ID

64 bits

Unicast prefix

64 bits

FF02:

24 bits

:1:FF0:0:0:0


Anycast IPv6 Addresses

Not associated with any prefix Summary and host routes are used to

locate nearest anycast group member Subnet router anycast address:

Subnet Prefix 000 . . . 000

n bits 128 - n bits


IPv6 Addresses for a Host

Unicast addresses: A link-local address for each interface Unicast addresses for each interface (site-local

or global addresses) A loopback address (::1)

Multicast addresses: The node-local scope all-nodes multicast

address (FF01::1) The link-local scope all-nodes multicast address

(FF02::1) The solicited-node address for each unicast

address The multicast addresses of joined groups


IPv6 Addresses for a Router Unicast addresses:

A link-local address for each interface Unicast addresses for each interface Loopback address (::1)

Anycast addresses Subnet-router anycast address Additional anycast addresses (optional)

Multicast addresses: The node-local scope all-nodes multicast address (FF01::1) The node-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 The multicast addresses of joined groups


Subnetting the IPv6 Address Space

Subdividing by using high-order bits that do not already have fixed values to create subnetted network prefixes

Two-step process:1. Determine the number of bits to be used for the

subnetting

2. Enumerate the new subnetted network prefixes


Subnetting for NLA IDs

Hexadecimal method Decimal method

[16-bit prefix]:00 ::

f

s

r


Subnetting for SLA IDs

Hexadecimal method Decimal method

[48-bit prefix]: ::

f

s

r


IPv6 Interface Identifiers

The last 64 bits of unicast IPv6 addresses

Interface identifier based on: Extended Unique Identifier (EUI)-64 address

Either assigned to a network adapter card or derived from IEEE 802 addresses

Temporarily assigned, randomly generated value that changes over time

A value assigned by a stateful address configuration protocol

A value assigned during a Point-to-Point Protocol connection establishment

A manually configured value


IEEE 802 Addresses

Company ID Extension ID U/L bit (u)

Universally (=0)/Locally (=1) Administered

U/G bit (g) Unicast (=0)/Group (=1) Address

ccccccug cccccccc cccccccc

24 bits 24 bits

xxxxxxxx xxxxxxxx xxxxxxxx

IEEE-administered company ID Manufacturer-selected extension ID


IEEE EUI-64 Addresses

Extended Unique Identifier Company ID Extension ID


24 bits 40 bits

xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx



Conversion of an IEEE 802 Address to an EUI-64 Address


24 bits 24 bits


ccccccug cccccccc cccccccc xxxxxxxx xxxxxxxx xxxxxxxx11111111 11111110

0xFF 0xFE


EUI-64 Address

IEEE 802 Address


Conversion of an EUI-64 Address to an IPv6 Interface ID

ccccccug cccccccc cccccccc xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx

EUI-64 Address

ccccccUg cccccccc cccccccc xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx

IPv6 Interface Identifier

Complement the universally/locally administered (U/L) bit


Conversion of an IEEE 802 Address to an IPv6 Interface ID

cccccc00 cccccccc cccccccc xxxxxxxx xxxxxxxx xxxxxxxx11111111 11111110

0xFF 0xFE

EUI-64 Address

cccccc00 cccccccc cccccccc

24 bits 24 bits



IEEE 802 Address

cccccc10 cccccccc cccccccc

64 bits

11111111 11111110 xxxxxxxx xxxxxxxx xxxxxxxx

IPv6 Interface Identifier


IEEE 802 Address Conversion Example

Host A has the MAC address of 00-AA-00-3F-2A-1C 1. Convert to EUI-64 format

00-AA-00-FF-FE-3F-2A-1C

2. Complement the U/L bit The first byte in binary form is 00000000. When the seventh bit is

complemented, it becomes 00000010 (0x02). Result is 02-AA-00-FF-FE-3F-2A-1C

3. Convert to colon hexadecimal notation 2AA:FF:FE3F:2A1C

Link-local address for node with the MAC address of 00-AA-00-3F-2A-1C is FE80::2AA:FF:FE3F:2A1C.


Temporary Address Interface Identifiers

Random IPv6 interface identifier Prevent identification of traffic regardless of the

prefix Initial value based on random number Future values based on MD5 hash of history

value and EUI-64-based interface identifier

Result is a temporary address Generated from public address prefixes using

stateless address autoconfiguration Changes over time


Mapping IPv6 Multicast Addresses to Ethernet Addresses

IPv6 Multicast Address

33-33-

8 16 24 32

FF...:

Ethernet Multicast Address


IPv4 Addresses and IPv6 Equivalents

IPv4 Address IPv6 AddressInternet address classes N/AMulticast addresses (224.0.0.0/4) IPv6 multicast addresses (FF00::/8)Broadcast addresses N/AUnspecified address is 0.0.0.0 Unspecified address is ::Loopback address is 127.0.0.1 Loopback address is ::1Public IP addresses Aggregatable global unicast

addressesPrivate IP addresses Site-local addresses (FEC0::/48)APIPA addresses Link-local addresses (FE80::/64)Dotted decimal notation Colon hexadecimal formatSubnet mask or prefix length Prefix length notation only


Review

IPv6 address space IPv6 address syntax Unicast IPv6 addresses Multicast IPv6 addresses Anycast IPv6 addresses IPv6 interface identifiers IPv4 addresses and IPv6 equivalents

Documents

Understanding IPv6 Slide: 1 Lesson 3 IPv6 Addressing