NET 125 Module 12 - IPv6 addressing

IPv6 has a much larger __ bit space

128

The ____ has created various protocols and tools to help network administrators

migrate their networks to IPv6

IETF

The IETF has created various protocols and tools to help network administrators migrate their networks to IPv6. These migration techniques can be divided into three categories: Dual stack

The devices run both IPv4 and IPv6 protocol stacks simultaneously

The IETF has created various protocols and tools to help network administrators migrate their networks to IPv6. These migration techniques can be divided into three categories: Tunneling

method of transporting an IPv6 packet over an IPv4 network. The IPv6

packet is encapsulated inside an IPv4 packet

The IETF has created various protocols and tools to help network administrators migrate their networks to IPv6. These migration techniques can be divided into three categories: Translation

Network Address Translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4

The first rule to help reduce the notation of IPv6 addresses is to omit any leading 0s (zeros)

Type Format

Preferred 2001 : 0db8 : 0000 : 1111 : 0000 : 0000 : 0000 : 0200

No leading zeros 2001 : db8 : 0 : 1111 : 0 : 0 : 0 : 200

Rule 2 – Double Colon A double colon (::) can replace

any single, contiguous string of one or more 16-bit hextets consisting of all zeros

There are three broad categories of IPv6 addresses:

• Unicast

Unicast uniquely identifies an interface on an IPv6-enabled device

There are three broad categories of IPv6 addresses:

• Multicast

Multicast is used to send a single IPv6 packet to multiple destinations

There are three broad categories of IPv6 addresses:

• Anycast

This is any IPv6 unicast address that can be assigned to multiple devices. A packet sent to an anycast address is routed to the nearest device having that address.

T or F: Unlike IPv4, IPv6 does not have a broadcast address. However, there is an IPv6 all-
nodes multicast address that essentially gives the same result

True

Prefix length is represented in slash notation and is used to indicate the network portion of an IPv6 address. The IPv6 prefix length can range from 0 to ___

128

The recommended IPv6 prefix length for LANs and most other types of networks is

/64

Unlike IPv4 devices that have only a single
address, IPv6 addresses typically have two
unicast addresses:

• Global Unicast Address (GUA)

• Link-local Address (LLA)

Unlike IPv4 devices that have only a single address, IPv6 addresses typically have two unicast addresses: Global Unicast Address (GUA)

This is similar to a public IPv4 address. These are globally unique, internet-routable addresses.

Unlike IPv4 devices that have only a single address, IPv6 addresses typically have two unicast addresses: Link-local Address (LLA)

Required for every IPv6-enabled device and used to communicate with other devices on the same local link. LLAs are not routable and are confined to a single link

Unique local addresses are used for

local addressing within a site or between a

limited number of sites.

• Unique local addresses can be used for devices that will never need to access

another network.

• Unique local addresses are not globally routed or translated to a global IPv6

address

IPv6 global unicast addresses (GUAs) are

globally unique and routable on the IPv6

internet

Currently, only GUAs

with the first three bits of 001 or 2000::/3 are being assigned.

• Currently available GUAs begins with a decimal 2 or a 3 (This is only 1/8th of the total

available IPv6 address space).

IPv6 GUA Structure: global routing prefix

prefix, or network, portion of the address that is

assigned by the provider, such as an ISP, to a customer or site. The global routing

prefix will vary depending on ISP policies

IPv6 GUA Structure: Subnet ID

the Subnet ID field is the area between the Global Routing Prefix and the

Interface ID. The Subnet ID is used by an organization to identify subnets within

its site

IPv6 GUA Structure: Interface ID

The IPv6 interface ID is equivalent to the host portion of an IPv4 address. It is

strongly recommended that in most cases /64 subnets should be used, which

creates a 64-bit interface ID

Note: IPv6 allows the

all-0s and all-1s host addresses can be assigned to a device. The all-0s address is

reserved as a Subnet-Router anycast address, and should be assigned only to routers

An IPv6 link-local address (LLA) enables a device to

communicate with other IPv6-

enabled devices on the same link and only on that link (subnet).

Packets with a source or destination LLA cannot be

routed

Every IPv6-enabled network interface must have an

LLA

If an LLA is not configured manually on an interface, the device will automatically create

one

IPv6 LLAs are in the ____ range

fe80::/10

The example shows commands to configure a GUA on the G0/0/0 interface on R1:

R1(config)# interface gigabitethernet 0/0/0
R1(config-if)# ipv6 address 2001:db8:acad:1::1/64
R1(config-if)# no shutdown
R1(config-if)# exit

The example shows commands to configure a LLA on the G0/0/0 interface on R1:

R1(config)# interface gigabitethernet 0/0/0
R1(config-if)# ipv6 address fe80::1:1 link-local
R1(config-if)# no shutdown
R1(config-if)# exit

Devices obtain GUA addresses dynamically through

Internet Control Message Protocol

version 6 (ICMPv6) messages

Router Solicitation (RS) messages are sent by

host devices to discover IPv6 routers

Router Advertisement (RA) messages are sent by

routers to inform hosts on how to obtain an IPv6 GUA and provide useful network information such as:

• Network prefix and prefix length

• Default gateway address

• DNS addresses and domain name

The RA can provide three methods for configuring an IPv6 GUA:

• SLAAC

• SLAAC with stateless DHCPv6 server

• Stateful DHCPv6 (no SLAAC)

SLAAC allows a device to configure a GUA without the services of

DHCPv6

Method 1: SLAAC: Devices obtain the necessary information to configure a GUA from the ICMPv6 RA messages of the

local router

Method 1: SLAAC: The prefix is provided by the RA and the device uses either the EUI-64 or random

generation method to create an interface ID

Method 2: SLAAC and Stateless DHCP

An RA can instruct a device to use both SLAAC and stateless DHCPv6.

The RA message suggests devices use the following:

• SLAAC to create its own IPv6 GUA

• The router LLA, which is the RA source IPv6 address, as the default gateway address

• A stateless DHCPv6 server to obtain other information such as a DNS server address and a domain name

Method 3: Stateful DHCPv6:

An RA can instruct a device to use stateful DHCPv6 only.

Stateful DHCPv6 is similar to DHCP for IPv4. A device can automatically receive a GUA, prefix length, and the addresses of DNS servers from a stateful DHCPv6 server.

The RA message suggests devices use the following:

• The router LLA, which is the RA source IPv6 address, for the default gateway

address.

• A stateful DHCPv6 server to obtain a GUA, DNS server address, domain name and

other necessary information.

When the RA message is either

SLAAC or SLAAC with stateless

DHCPv6, the client must

generate its own interface ID

The interface ID can be created
using the EUI-64 process or a
randomly generated 64-bit
number

EUI-64 Process

The IEEE defined the Extended Unique Identifier (EUI) or modified EUI-64 process

which performs the following:

A 16 bit value of fffe (in hexadecimal) is inserted into the middle of the 48-bit

Ethernet MAC address of the client.

• The 7th bit of the client MAC address is reversed from binary 0 to 1.

• Example:

48-bit MAC- fc:99:47:75:ce:e0

EUI-64 Interface ID- fe:99:47:ff:fe:75:ce:e0

All IPv6 interfaces must have an

IPv6 LLA

The figure shows the LLA is dynamically created using the fe80::/10 prefix and the

interface ID using the EUI-64 process, or a randomly generated

64-bit number

IPv6 multicast addresses have the prefix ff00::/8. There are two types of IPv6 multicast addresses:

• Well-Known multicast addresses

• Solicited node multicast addresses

Note: Multicast addresses can only be destination addresses and not source addresses

Well-known IPv6 multicast addresses are assigned and are reserved for predefined
groups of devices.
There are two common IPv6 Assigned multicast groups:

• ff02::1 All-nodes multicast group

• ff02::2 All-routers multicast group

There are two common IPv6 Assigned multicast groups: ff02::1 All-nodes multicast group

This is a multicast group that all IPv6-enabled devices
join. A packet sent to this group is received and processed by all IPv6 interfaces on the link
or network

There are two common IPv6 Assigned multicast groups:

This is a multicast group that all IPv6 routers join. A

router becomes a member of this group when it is enabled as an IPv6 router with the ipv6

unicast-routing global configuration command

A solicited-node multicast address

is mapped to a special

Ethernet

multicast address

IPv6 was designed with subnetting in mind.

• A separate subnet ID field in the IPv6 GUA is used to create

subnets

IPv6 was designed with subnetting in mind.

the subnet ID field is the area between the Global Routing Prefix and the

interface ID

Given the 2001:db8:acad::/48 global

routing prefix with a 16 bit subnet ID.

• Allows 65,536 /64 subnets

• The global routing prefix is the

same for all subnets.

Only the subnet ID hextet is

incremented in hexadecimal for each

subnet.

The example topology requires five subnets, one for each LAN as well as for the serial link

between R1 and R2

The five IPv6 subnets were allocated, with the subnet ID field 0001 through 0005. Each /64

subnet will provide more addresses than will ever be needed

The IETF has created various protocols and tools to help network administrators migrate their

networks to

IPv6. The migration techniques can be divided into three categories: dual stack,

tunneling, and translation

There are three types of IPv6 addresses:

unicast, multicast, and anycast

An IPv6 unicast address uniquely identifies an interface on an

IPv6-enabled device

IPv6 global unicast addresses (GUAs) are globally unique and routable on the

IPv6 internet

An IPv6 link-local address (LLA) enables a device to communicate with other

IPv6-enabled

devices on the same link and only on that link (subnet)

A device obtains a GUA dynamically through ICMPv6 messages. IPv6 routers periodically send

out ICMPv6 RA messages

every 200 seconds, to all IPv6-enabled devices on the network

RA messages have three methods:

SLAAC, SLAAC with a stateless DHCPv6 server, and stateful

DHCPv6 (no SLAAC)

The interface ID can be created using the EUI-64 process or a randomly

generated 64-bit number

The EUIs process uses the 48-bit Ethernet MAC address of the client and inserts another

16 bits in
the middle of MAC address to create a 64-bit interface ID

All IPv6 devices must have an IPv6 LLA. An LLA can be configured manually or

created
dynamically

There are two types of IPv6 multicast addresses:

well-known multicast addresses and solicited

node multicast addresses

Two commonIPv6 assigned multicast groups are:

ff02::1 All-nodes multicast group and ff02::2 All-

routers multicast group

A solicited-node multicast address is similar to the all-nodes

multicast address. The advantage of a

solicited-node multicast address is that it is mapped to a special Ethernet multicast address

IPv6 was designed with subnetting in mind. A separate subnet ID field in the

IPv6 GUA is used to

create subnets