IPv6 address Introduction

1. Recognize IPv6 addresses

An IPv4 address is in a format similar to a. B .c.d. It is a 32-bit IPv4 address \". \ "is divided into four segments and expressed in decimal format. IPv6 addresses are similar to the format of X: X, which is 128 bits, it is divided into 8 segments by \ ": \" and expressed in hexadecimal notation. It can be seen that the IPv6 address space is greatly expanded compared with the IPv4 address space.

The IPv6 address is defined in rfc2373 in detail. According to the definition, a complete IPv6 address representation: xxxx

Example: 2001: 0000: 1f 1f: 0000: 0000: 0100: 11A 0: addf

To simplify the expression, rfc2373 proposes that the first 0 in each segment can be omitted, and the continuous 0 can be omitted as \ ": \", but only once. For example:

1080: 0: 0: 0: 8: 800: 200C: Jun A can be abbreviated as 1080: 8: 800: 200C: Jun

Ff01: 0: 0: 0: 0: 0: 0: 101 can be abbreviated as ff01: 101

0: 0: 0: 0: 0: 0: 0: 1 can be abbreviated as: 1

0: 0: 0: 0: 0: 0: 0: 0 can be abbreviated ::

Similar to cdir in IPv4, IPv6 uses a prefix to represent the network address space, for example:

2001: 251: e000:/48 indicates the address space with a prefix of 48 bits. The last 80 bits can be allocated to the host on the network, with a total address of 2 to the power of 80.

To better understand IPv6, a table is provided here to compare the ing between IPv4 addresses and IPv6 addresses.

IPv4 address

IPv6 address

Multicast address (224.0.0.0/4)

IPv6 multicast address (ff00:/8)

Broadcast address

None. Only anycast addresses are available.

The unspecified address is 0.0.0. 0.

The unspecified address is ::

The loop address is 127.0.0.1.

Loop address: 1

Public IP Address

Global unicast addresses can be aggregated

Private address (10.0.0. 0/8, 172.16.0.0/12, and 192.168.0.0/16)

Local site address (fec0:/48)

Address automatically configured by Microsoft auto-dedicated IP address (169.254.0.0/16)

Local link address (fe80:/64)

Expression: dotted-decimal

Expression: Colon hexadecimal (uncompress)

Subnet Mask representation: In dot matrix decimal notation or prefix length notation (CIDR)

Subnet Mask representation: only use the prefix length representation (CIDR)

2. IPv6 address scope and address classification

? An IPv6 address is specified to an interface. An interface can specify multiple addresses.

? IPv6 addresses have the following scopes:

Link local address valid for this link

The site local address is valid in this region (SITE). A site is usually a campus network.

The global address is globally valid, and the global unicast address can be aggregated.

? IPv6 address classification:

Unicast (spof) Address

Multicast multicast address

Anycast multicast address (transmitted by any point)

IPv6 does not define a broadcast address. Its function is replaced by a multicast address.

3. Common IPv6 addresses and their prefixes

?:/1280: 0: 0: 0: 0: 0: 0: 0: 0. It can only serve as the source address of the host that has not yet obtained the official address. It cannot be used as the destination address, cannot be assigned to real network interfaces.

?: 1/1280: 0: 0: 0: 0: 0: 0: 1: return address, which is equivalent to localhost (127.0.0.1) in IPv4. Ping locahost to obtain this address.

?2001:/16Globally aggregated addresses, which are allocated by region and ISP by IANA. They are the most common IPv6 addresses and are unicast addresses.

?2002:/16Address 6 to 4, used for 6to4 to automatically construct the address of the tunnel technology, which belongs to the unicast address.

?3ffe:/16The IPv6 6bone test network address in the early stage, which belongs to the unicast address.

?Fe80:/10Local link address, used for a single link, suitable for automatic configuration, neighboring machine discovery, etc., the router does not forward addresses starting with fe80.

?Ff00:/8Multicast address.

?: A. B .c.dAn IPv6 address compatible with IPv4, where <a. B .c.d> represents an IPv4 address. The IPv4/IPv6 nodes that automatically send the IPv6 packet in the IPv4 network tunnel will use these addresses.

?: FFFF: a. B .c.dIs the IPv6 address mapped from IPv4, where <a. B .c.d> represents the IPv4 address, for example: FFFF: 202.120.2.30, which is used to represent IPv4 nodes on networks that do not support IPv6.

4. integrated networking technology

When IPv6 and IPv4 coexist, the following comprehensive networking technologies and strategies are available for interconnection between V4 and V6:

1) Dual Stack Policy

A dual-stack policy is a network element that has both IPv4 and IPv6 protocol stacks. It can receive, process, and send and receive IPv4 groups, as well as receive, process, and send and receive IPv6 groups. For a host (terminal), "dual-stack" means that it can encapsulate IPv4 or IPv6 data generated by the business as needed. For a router, "dual-stack" means to maintain the IPv6 and IPv4 route protocol stacks in a router device, so that the router can communicate with IPv4 hosts and IPv6 hosts, supports independent IPv6 and IPv4 routing protocols. IPv4 and IPv6 routing information is calculated based on their respective routing protocols to maintain different route tables. IPv6 datagram is forwarded according to the route table obtained by the IPv6 routing protocol, and IPv4 datagram is forwarded according to the route table obtained by the IPv4 routing protocol.

2) tunnel Policy

Tunnel policy is a common mechanism used in IPv4/v6 integrated networking technology. The so-called "Tunnel" is simply to use one protocol to transmit the data technology of another protocol. Tunnels include tunnel endpoints and tunnel endpoints, which are usually dual-stack nodes. The tunnel entry encapsulates and sends the data of another protocol in the form of a protocol. The protocol data received at the tunnel exit is unencapsulated and processed accordingly. Tunnel Entry usually requires maintenance of tunnel-related information, such as recording tunnel MTU parameters. At the exit of the tunnel, encapsulation data is usually filtered out for security reasons to prevent external malicious attacks.

Tunnel Configuration methods include Manual Tunnel Configuration and automatic tunnel configuration, and automatic tunnel configuration can be divided into compatible address automatic tunnel, 6to4 tunnel, 6over4, isatap, MPLS tunnel, GRE tunnel, etc, the implementation principles and technical details of these tunnels are different, and their application scenarios are also different.

IPv6 address Introduction