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This article mainly explains "what are the basic knowledge of IPv6". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what are the basics of IPv6".

The most fundamental change in IPv6 is to provide future requirements for globally identifiable address space. Mobile device-based applications such as personal digital devices (PDA), mobile phones, cars, home networks and other mobile data communication devices all require globally identifiable addresses.

1. IPv6 background

IPv6 expands the number of network address bits from 32 to 128 bits, which means that it can provide a unique and definite address for any device on the planet that needs to be connected to the Internet. With globally identifiable addresses, IPv6 provides global address reachability, end-to-end secure communication, and support for all address-demanding applications and services. In addition, the rich IPv6 address space eliminates the NAT (Network Address Translation) bottleneck in the network and improves the network efficiency.

II. IPv6 address format

Because the IPv6 address is 128 bits long, it is much more complex than the 32-bit IPv4 address. At present, the address of IPv6 is represented by a string of hexadecimal numbers, separated by a semicolon (:) every 16 bits, in the following format: x:x:x:x:x:x:x:x.

Here are two examples of IPv6 addresses:

2001:0DB8:7654:3210:FEDC:BA98:7654:3210

1080:0:0:0:8:800:200C:417A

Typically, the IPv6 address contains consecutive zeros. To avoid the complexity of IPv6 address representation, consecutive zeros can be abbreviated to two colons (::). The abbreviated format of the able1 lists IPv6 address. Two colons can be used as part of an IPv6 address. You can configure multiple addresses on an interface, but only one link-local address. Note that the two colons (::) can only appear once in the IPv6 address and can only represent the longest consecutive 0.

Unicast Unicast address

An IPv6 unicast address is an interface used to identify a network node. When the destination address of a packet is a unicast address, it will be sent to the network interface marked with that address. An IPv6 router should support the following unicast address types:

Global aggregatable address: a global address that can be aggregated.

Site-local address: address within the area (proposal to remove by IETF)

Link-local address: link interface addr

IPv4-compatible IPv6 address: IPv4 compliant address

1. Global address that can be aggregated

An aggregable global address is an address with a globalized aggregable IPv6 prefix. This structured and globalized unicast address can carry out strict aggregation of routing prefixes, which can greatly reduce the number of routes in the whole routing table and reduce the complexity of routing. Aggregable global addresses are used to identify link addresses and can perform multi-level route aggregation all the way to the top Internet service provider (ISPs). Globalized aggregable IPv6 addresses are defined as globalized routing prefixes, subnetwork numbers, and interface addresses. Except for addresses that start with binary 000, all global IPv6 unicast addresses have 64-bit interface addresses. At present, the allocation range of global unicast addresses starts with binary 001 (2000 rigor bank 3).

2. Site-Local address

A site-local address is an IPv6 unicast address with a prefix FEC0::/10 and a 16-bit subnet number plus 64-bit EUI-64. Site-local addresses are very similar to the private address space 10.0.0.0 in IPv4; routes can be looked up within an area without the need for a globalized unique address prefix. An Site-local address can be considered a private address because it can only be used in a strictly restricted area.

3. Link-Local address

The link-local address is an IPv6 unicast address with the link-local prefix FE80::/10 (1111 1110 10), which is automatically generated using the modified EUI-64 address format. Link-local addresses can be used for neighbor Discovery Protocol (neighbor discovery protocol) and stateless autoconfiguration processes. Nodes on the same link can communicate using link-local addresses; there is no need for site-local addresses or globalized unicast addresses.

4. IPv4-compatible IPv6 address

An IPv4-compatible IPv6 address is an IPv6 unicast address with a high 96-bit all-zero and a low 32-bit IPv4 address. This IPv4-compatible IPv6 address can be expressed as 0:0:0:0:0:0:A.B.C.D or:: A.B.C.D. The entire 128bit IPv4-compatible IPv6 address is the lower 32-bit that inserts the IPv4 address of the network node directly into the IPv6 address. IPv4-compatible IPv6 addresses are used to use automatic tunneling (tunnels) when running IPv4 and IPv6 dual stacks.

5. IPv6 address type: Anycast address

An anycast address is the address of an IPv6 that belongs to an interface of multiple network nodes. A packet with the anycast address as the destination is forwarded to the nearest network interface; the distance of the interface is determined by the calculation of the route. Anycast addresses are inseparable from unicast addresses in terms of address structure, because anycast addresses exist in the address space of unicast addresses. But when a unicast address can be received by more than one network interface, it is an anycast address. The Anycast address needs to be clearly defined on the network node: this address is an anycast address.

6. IPv6 address type: multicast address Multicast

The IPv6 address of a prefix FF00::/8 (1111 1111) indicates that it is an IPv6 multicast address. When the destination address of a packet is a multicast address, it will be copied and forwarded to recipients of multiple networks. The second octal number of the multicast address prefix represents the range of the multicast address. The octal number is divided into two parts: the first four digits 0000 represent a permanent multicast address, the first four bits 0001 represent temporary multicast addresses, and the last four bits represent the multicast range, which currently defines 1, 2, 5, 8, and or E, respectively, representing different multicast ranges. As shown in Figure6. For example, a multicast address prefixed with FF02::/16 represents a permanent multicast address in the link range.

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