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Global Address

A global address uniquely identifies a device on the Internet. It is similar to a “public IP address” in

IPv4. A global unicast address starts with a 2 or 3.

Unspecified Address

An unspecified address (0:0:0:0:0:0:0:0 or ::) is used as the source address when a device does

not have its own address. It is similar to “0.0.0.0” in IPv4.

Loopback Address

A loopback address (0:0:0:0:0:0:0:1 or ::1) allows a host to send packets to itself. It is similar to

“127.0.0.1” in IPv4.

Multicast Address

In IPv6, multicast addresses provide the same functionality as IPv4 broadcast addresses.

Broadcasting is not supported in IPv6. A multicast address allows a host to send packets to all hosts

in a multicast group.

Multicast scope allows you to determine the size of the multicast group. A multicast address has a

predefined prefix of ff00::/8. The following table describes some of the predefined multicast

addresses.

The following table describes the multicast addresses which are reserved and can not be assigned

to a multicast group.

Table 110

Predefined Multicast Address

MULTICAST ADDRESS

DESCRIPTION

FF01:0:0:0:0:0:0:1

All hosts on a local node.

FF01:0:0:0:0:0:0:2

All routers on a local node.

FF02:0:0:0:0:0:0:1

All hosts on a local connected link.

FF02:0:0:0:0:0:0:2

All routers on a local connected link.

FF05:0:0:0:0:0:0:2

All routers on a local site.

FF05:0:0:0:0:0:1:3

All DHCP severs on a local site.

Table 111

Reserved Multicast Address

MULTICAST ADDRESS

FF00:0:0:0:0:0:0:0

FF01:0:0:0:0:0:0:0

FF02:0:0:0:0:0:0:0

FF03:0:0:0:0:0:0:0

FF04:0:0:0:0:0:0:0

FF05:0:0:0:0:0:0:0

FF06:0:0:0:0:0:0:0

FF07:0:0:0:0:0:0:0

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Subnet Masking

Both an IPv6 address and IPv6 subnet mask compose of 128-bit binary digits, which are divided

into eight 16-bit blocks and written in hexadecimal notation. Hexadecimal uses four bits for each

character (1 ~ 10, A ~ F). Each block’s 16 bits are then represented by four hexadecimal

characters. For example, FFFF:FFFF:FFFF:FFFF:FC00:0000:0000:0000.

Interface ID

In IPv6, an interface ID is a 64-bit identifier. It identifies a physical interface (for example, an

Ethernet port) or a virtual interface (for example, the management IP address for a VLAN). One

interface should have a unique interface ID.

EUI-64

The EUI-64 (Extended Unique Identifier) defined by the IEEE (Institute of Electrical and Electronics

Engineers) is an interface ID format designed to adapt with IPv6. It is derived from the 48-bit (6-

byte) Ethernet MAC address as shown next. EUI-64 inserts the hex digits fffe between the third and

fourth bytes of the MAC address and complements the seventh bit of the first byte of the MAC

address. See the following example.

Stateless Autoconfiguration

With stateless autoconfiguration in IPv6, addresses can be uniquely and automatically generated.

Unlike DHCPv6 (Dynamic Host Configuration Protocol version six) which is used in IPv6 stateful

autoconfiguration, the owner and status of addresses don’t need to be maintained by a DHCP

server. Every IPv6 device is able to generate its own and unique IP address automatically when

IPv6 is initiated on its interface. It combines the prefix and the interface ID (generated from its own

Ethernet MAC address, see

Interface ID

and

EUI-64

) to form a complete IPv6 address.

When IPv6 is enabled on a device, its interface automatically generates a link-local address

(beginning with fe80).

When the interface is connected to a network with a router and the AMG1302/AMG1202-TSeries is

set to automatically obtain an IPv6 network prefix from the router for the interface, it generates

FF08:0:0:0:0:0:0:0

FF09:0:0:0:0:0:0:0

FF0A:0:0:0:0:0:0:0

FF0B:0:0:0:0:0:0:0

FF0C:0:0:0:0:0:0:0

FF0D:0:0:0:0:0:0:0

FF0E:0:0:0:0:0:0:0

FF0F:0:0:0:0:0:0:0

Table 111

Reserved Multicast Address (continued)

MULTICAST ADDRESS

MAC

00

: 13

: 49

: 12

: 34

: 56

EUI-64

0

2

: 13

: 49

:

FF

:

FE

: 12

: 34

: 56

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3

another address which combines its interface ID and global and subnet information advertised

from the router. This is a routable global IP address.

DHCPv6

The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, RFC 3315) is a server-client protocol

that allows a DHCP server to assign and pass IPv6 network addresses, prefixes and other

configuration information to DHCP clients. DHCPv6 servers and clients exchange DHCP messages

using UDP.

Each DHCP client and server has a unique DHCP Unique IDentifier (DUID), which is used for

identification when they are exchanging DHCPv6 messages. The DUID is generated from the MAC

address, time, vendor assigned ID and/or the vendor's private enterprise number registered with

the IANA. It should not change over time even after you reboot the device.

Identity Association

An Identity Association (IA) is a collection of addresses assigned to a DHCP client, through which

the server and client can manage a set of related IP addresses. Each IA must be associated with

exactly one interface. The DHCP client uses the IA assigned to an interface to obtain configuration

from a DHCP server for that interface. Each IA consists of a unique IAID and associated IP

information.

The IA type is the type of address in the IA. Each IA holds one type of address. IA_NA means an

identity association for non-temporary addresses and IA_TA is an identity association for temporary

addresses. An IA_NA option contains the T1 and T2 fields, but an IA_TA option does not. The

DHCPv6 server uses T1 and T2 to control the time at which the client contacts with the server to

extend the lifetimes on any addresses in the IA_NA before the lifetimes expire. After T1, the client

sends the server (

S1

) (from which the addresses in the IA_NA were obtained) a Renew message. If

the time T2 is reached and the server does not respond, the client sends a Rebind message to any

available server (

S2

). For an IA_TA, the client may send a Renew or Rebind message at the client's

discretion.

DHCP Relay Agent

A DHCP relay agent is on the same network as the DHCP clients and helps forward messages

between the DHCP server and clients. When a client cannot use its link-local address and a well-

known multicast address to locate a DHCP server on its network, it then needs a DHCP relay agent

to send a message to a DHCP server that is not attached to the same network.

The DHCP relay agent can add the remote identification (remote-ID) option and the interface-ID

option to the Relay-Forward DHCPv6 messages. The remote-ID option carries a user-defined string,

3.

In IPv6, all network interfaces can be associated with several addresses.

T1

T2

Renew

Rebind

Rebind

to S1

Renew

to S1

Renew

to S1

Renew

to S1

Renew

to S1

Renew

to S1

to S2

to S2

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such as the system name. The interface-ID option provides slot number, port information and the

VLAN ID to the DHCPv6 server. The remote-ID option (if any) is stripped from the Relay-Reply

messages before the relay agent sends the packets to the clients. The DHCP server copies the

interface-ID option from the Relay-Forward message into the Relay-Reply message and sends it to

the relay agent. The interface-ID should not change even after the relay agent restarts.

Prefix Delegation

Prefix delegation enables an IPv6 router to use the IPv6 prefix (network address) received from the

ISP (or a connected uplink router) for its LAN. The AMG1302/AMG1202-TSeries uses the received

IPv6 prefix (for example, 2001:db2::/48) to generate its LAN IP address. Through sending Router

Advertisements (RAs) regularly by multicast, the AMG1302/AMG1202-TSeries passes the IPv6

prefix information to its LAN hosts. The hosts then can use the prefix to generate their IPv6

addresses.

ICMPv6

Internet Control Message Protocol for IPv6 (ICMPv6 or ICMP for IPv6) is defined in RFC 4443.

ICMPv6 has a preceding Next Header value of 58, which is different from the value used to identify

ICMP for IPv4. ICMPv6 is an integral part of IPv6. IPv6 nodes use ICMPv6 to report errors

encountered in packet processing and perform other diagnostic functions, such as "ping".

Multicast Listener Discovery

The Multicast Listener Discovery (MLD) protocol (defined in RFC 2710) is derived from IPv4's

Internet Group Management Protocol version 2 (IGMPv2). MLD uses ICMPv6 message types, rather

than IGMP message types. MLDv1 is equivalent to IGMPv2 and MLDv2 is equivalent to IGMPv3.

MLD allows an IPv6 switch or router to discover the presence of MLD listeners who wish to receive

multicast packets and the IP addresses of multicast groups the hosts want to join on its network.

MLD snooping and MLD proxy are analogous to IGMP snooping and IGMP proxy in IPv4.

MLD filtering controls which multicast groups a port can join.

MLD Messages

A multicast router or switch periodically sends general queries to MLD hosts to update the multicast

forwarding table. When an MLD host wants to join a multicast group, it sends an MLD Report

message for that address.

An MLD Done message is equivalent to an IGMP Leave message. When an MLD host wants to leave

a multicast group, it can send a Done message to the router or switch. The router or switch then

sends a group-specific query to the port on which the Done message is received to determine if

other devices connected to this port should remain in the group.

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Transition Techniques

IPv6 Over IPv4 Tunnelling

To route traffic between two IPv6 networks over an IPv4 network, an IPv6 over IPv4 tunnel has to

be used.

On the AMG1302/AMG1202-TSeries, you can either set up a configured tunnel or an automatic 6to4

tunnel. The following describes each method.

Configured Tunnel

A configured tunnel is a point-to-point tunnelling mechanism that encapsulates an IPv6 address

with an IPv4 address. Routers (

A

and

B

) on both IPv6 networks (

1

and

2

) each must have an

interface that connects to the IPv4 network (with an IPv4 address). This allows the router to send

and receive IPv6 data over the IPv4 network.

In this case, you must specify

B

’s public IPv4 address on

A

(similarly, specify

A

’s public IPv4

address on

B

) in order for packets to arrive at the intended destination through the IPv4 network.

Figure 178

Configured Tunnel Example

6to4 Tunnel

A 6to4 tunnel is an automatic tunnelling mechanism that provides connection between IPv6

networks across an IPv4 network. To transmit IPv6 packets over an IPv4 network, the IPv6 packets

are encapsulated inside IPv4 packets.

The following figure shows a network example.

Figure 179

6to4 Relay Router Network Example

In a 6to4 tunnel, 6to4 routers (

A

and

B

in the example network) forward these packets between

IPv6 networks (

1

and

2

) over the IPv4 Internet. A 6to4 relay router (

C

) connects to both an IPv6