IPv6 address format and text Representation

In order to expand the network, we use the IPv6 protocol. As an improvement of the previous version protocol, the address type in the traditional sense is no longer applicable, now let's analyze the types of IPv6 addresses and basic knowledge about text representation.

The leading position in the address defines the specific IPv6 address type. A variable-length field containing the leading bits is called the format prefix FP ). Different address types have different functions.

IPv6 address type

In RFC 2373, several IPv6 addressing schemes are specified ). The IPv6 address is the 128-bit identifier of the interface and interface set. RFC 2373 defines multiple address formats for IPv6. IPv6 addresses are roughly divided into the following types:

Unicast: the address of a single interface. The packet sent to the unicast address is sent to the interface identified by this address.

Arbitrary playback: the address of a group of interfaces. In most cases, these interfaces belong to different nodes. Packets sent to any broadcast address are sent to one of the interfaces identified by this address. Since the use of any broadcast address standards are still being improved, so the current HP-UX does not support any broadcast.

Multicast: the addresses of a group of interfaces generally belong to different nodes ). Packets sent to multicast addresses are sent to each interface identified by this address. Unlike IPv4, there is no broadcast address in IPv6, because this function has been replaced by the multicast function.

IPv6 address text Representation

There are three common formats used to express IPv6 addresses in the form of text strings:

The first form is x: x, where "x" is a hexadecimal value, it corresponds to eight 16-bit segments in the 128-bit address respectively. Example: 2001: fecd: ba23: cd1f: dcb1: 1010: 9234: 4088.

Some IPv6 addresses may contain a long string of digits. A special syntax is developed to describe the address in text. ":" Indicates that there are multiple 16-bit zeros. ":" Can only appear once in an address. It can be used to compress leading, ending, or adjacent 16-bit zeros in an address. For example, fec0: 1: 0: 0: 0: 0: 1234 can be expressed as fec0: 1: 1234.

When processing a hybrid environment with IPv4 and IPv6 nodes, you can use another form of IPv6 address. X: d. d. d. d. "x" indicates the hexadecimal value of the 96-bit high-order byte of the IPv6 address, and "d" indicates the decimal value of the 32-bit low-order byte. Generally, the "IPv6 address mapped to IPv4" and "IPv6 address compatible with IPv4" can be expressed in this notation. Example: 0: 0: 0: 0: 0: 0: 10.1.2.3 and: 10.11.3.123

IPv6 address Prefix: the IPv6 address prefix is similar to the CIDR in IPv4 and is written into the CIDR representation. The IPv6 address prefix is represented by this notation: IPv6-address/prefix-length where the IPv6-address is an IPv6 address expressed in any of the preceding notation, "prefix-length" is a decimal value, indicating the number of leftmost adjacent digits of the prefix. For example, fec0: 0: 0: 1: 1234/64. The first 64-bit "fec0: 0: 0: 1" of the address constitutes the prefix of the address. In an IPv6 address, the address prefix is used to indicate the number of digits in the IPv6 address to indicate the subnet.

Unicast address: IPv6 unicast addresses can be classified into multiple types: globally clustered unicast addresses, local site addresses, and local link addresses. The interface identifier in the IPv6 unicast address is used to identify the interface in the link. The interface identifier must be unique in this link. A link is usually identified by a subnet prefix. If all bits of a unicast address are zero, this address is called an unspecified address. It is represented as ":" In text format. The Unicast address ": 1" or "0: 0: 0: 0: 0: 0: 0: 0: 1" is called the return address. The node uses the loopback address when sending data packets to itself.

Clustered global unicast address: a globally unique IPv6 address. In RFC 2374, this address format is fully defined as an IPv6 clustered global unicast address format ).

Example: ffff: 192.168.0.1

FP = Format prefix). For clustered global unicast addresses, the value is "001" tla id = Top-level Aggregation Identifier) RES = Reserved for future use) nla id = Next-Level Aggregation Identifier) sla id = Site-Level Aggregation Identifier) interface ID = Interface Identifier)

Local link address: the local link address is used to address nodes on a single link. Packets from or sent to the local link address are not forwarded by the router.

Local site address: the local site address should be used within the same site. The router does not forward any data packets from the local site source address or the destination address is the external site address.

Multicast address: the multicast address is the identifier of a group of nodes. "FF" at the beginning of the address identifies this address as a multicast address. The "flag" field is a group of four "000T ". The three digits in the high order are reserved bits and must be zero. The last "T" indicates whether it is permanently allocated. If the value is zero, it is permanently allocated; otherwise, it is temporarily allocated. The "range" field is a four-digit field used to limit the range of multicast groups. For example, the value "1" indicates that the multicast group is a local multicast group of a node. The value "2" indicates that the range is local to the link. The "group ID" field identifies multicast groups. The following are some common Multicast Groups:

All node addresses = FF02: 0: 0: 0: 0: 0: 0: 1 link local) All router addresses = FF02: 0: 0: 0: 0: 0: 0: 0: 0: 2 link local) All router addresses = FF05: 0: 0: 0: 0: 0: 0: 0: 2 site local)

The above section describes the IPv6 address type.