PLANET MH-2300 User Manual

Page 41

Gigabit Multi-Homing VPN Security Gateway

MH-2300

representation of a public IPv4 address), is used by IPv6/IPv4
nodes that are communicating with IPv6 over an IPv4
infrastructure. When the IPv4-compatible address is used as an
IPv6 destination, the IPv6 traffic is automatically encapsulated
with an IPv4 header and sent to the destination using the IPv4
infrastructure.

z IPv4-mapped addresses: The IPv4-mapped address,

0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z, represents an IPv4-only
node to an IPv6 node. For example, ::ffff:192.0.2.128 is the
IPv4-mapped IPv6 address for IPv4 address 192.0.2.128

The leading bits in the address define the specific IPv6 address type. The

variable-length field containing these leading bits is called a Format Prefix
(FP).

An IPv6 unicast address is divided into two parts. The first part

contains the address prefix (also known as subnet prefix such as
21DA:D3:0:2F3B::/64), and the second part contains the interface identifier
(MAC address).
A concise way to express an IPv6 address/prefix combination is as

follows: Ipv6-address/prefix-length. For example, an IPv6 address with
a 64-bit prefix is represented as 3FFE:FFFF:0:CD30:0:0:0:0/64 or
cormpressed as 3FFE:FFFF:0:CD30::/64.

Although

prefixes

can be defined along bit boundaries, the colon

hexadecimal notation for IPv6 addresses is expressed along nibble
(4-bit) boundaries. To properly express a subnet with a prefix where its
prefix length is not a multiple of 4, you must complete hexadecimal to
binary conversions to determine the appropriate subnet identifier. For
example, to express the subnet of the address and prefix of
21DA:D3:0:2F3B:2AA:FF:FE28:9C5A/59, you must convert the “3” in
“2F3B” to binary (0011), divide the nibble between the third and fourth
binary digits, and then convert back to hexadecimal. The result is the
subnet identifier of 21DA:D3:0:2F20::/59.

IPv6 address is classified into three types:

Unicast address:

z Link-local addresses: These addresses are used on a single link

and have the following format: FE80::InterfaceID. Link-local
addresses are used primarily at startup and when the system has
not yet acquired addresses of larger scope. They are analogous
to IPv4’s RFC 3927 addresses (169.254.0.0/16).

z Site-local addresses: These addresses are used on a single site

and have the following format: FEC0::SubnetID:InterfaceID. The
site-local addresses are used for addressing inside a site without
the need for a global prefix. They are analogous to IPv4's
RFC1918 addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).

z Global IPv6 unicast addresses: These addresses can be used

across the Internet and have the following format: 010 (FP, 3 bits)
TLA ID (13 bits) Reserved (8 bits) NLA ID (24 bits) SLA ID (16 bits)
InterfaceID (64 bits).

Multicast address: An identifier for a set of interfaces (typically

belonging to different nodes). A packet sent to this address is delivered