Reprinted from: https://tieba.baidu.com/p/3985626373
The address length of IPv6 is 128 bits (bit).
Divide the 128-bit address into segments of 16 bits each, converting each segment to a hexadecimal number, separated by colons.
For example: 2000:0000:0000:0000:0001:2345:6789:abcd
This address is very long. Two methods can be used to compress this address.
Leading zero compression method:
omit the leading zeros of each segment, but each segment is There should be at least one number
Example: 2000:0:0:0:1:2345:6789:abcd
Double colon method:
If an IPv6 address expressed in colon hexadecimal notation, if several consecutive segment values are all 0, then these 0s can be abbreviated as ::. There can only be one :: in each address.
For example: 2000::1:2345:6789:abcd
Unicast Address (Unicast IPv6Addresses)
Aggregatable Global Unicast Addresses (Aggregatable Global UnicastAddresses)
can be routable and reachable on a global scale, equivalent to globaladdresses in IPv4. The first three bits are 001.
For example: 2000::1:2345:6789:abcd
Link-LocalAddresses
are used for communication between adjacent nodes on the same link, which is equivalent to 169.254.0.0 in IPv4 /16 address. IPv6 routers do not forward packets with link-local addresses. The first 10 bits are 1111 111010. Since the last is the 64-bit interfaceID, its prefix is always FE80::/64
. For example: FE80::1
Site-Local Addresses
For local networks that cannot access the internet, you can use site-local addresses, which are equivalent to privateaddresses in IPv4 (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16). Its first 10 bits are 1111 111011, and it ends with a 16-bit SubnetID and a 64-bit interfaceID, so its prefix is FEC0::/48.
It's worth noting that in RFC3879, it was finally decided to drop unicast site-local addresses. The rationale for abandonment is that the complexity of unicast site-local addresses due to their inherent ambiguity outweighs their potential benefit. It was replaced by ULA in RFC4193.
Unique Local IPv6 Unicast Address (ULA, Unique Local IPv6 Unicast Address)
is an address standardized in RFC4193 to replace unicast site-local addresses in local communications. ULA has a fixed prefix of FD00::/8 followed by a 40-bit random identifier called the global ID.
Unspecified address (Unspecified address)
0:0:0:0:0:0:0:0 or ::
When a valid address cannot be determined, the unspecified address is generally used as the source address. An unspecified address cannot be used as a destination address.
Loopback address (Loopbackaddress)
The loopback address::1 is used to identify a loopback interface, which enables a node to send data packets to itself. Equivalent to the IPv4 loopback address 127.0.0.1
IPv4-compatible address (IPv4-compatibleaddress)
The form is ::wx,yz, where wxyz is the decimal point notation of the IPv4 public address, which is used for IPv6/IPv4 nodes (both supported) to communicate using IPv6 protocols on networks that only support IPv4.
But this technique turned out to be a bad idea, and the use of such addresses was deprecated in RFC4291.
The IPv4-mapped address (IPv4-mappedaddress)
is in the form of ::FFFF:wxyz, where wxyz is the decimal point notation of the IPv4 public address, which is used for an IPv4-only node to be represented as an IPv6 node
6over4 address
[64bit-prefix ]:0:0:WWXX:YYZZ, where WWXX:YYZZ is the decimal point notation of the wxyzIPv4 public address for a node that uses the 6to4 tunneling mechanism.
6to4 address
2002:WWXX:YYZZ:[SLAID]:[Interface ID], used to represent a tunnel mechanism node using the 6to4 protocol.
The first 8 bits of Multicast IPv6 Addresses
are 11111111, of
which the multicast addresses from FF01:: to FF0F:: are reserved private addresses
FF01::1 Node local range All nodes multicast address
FF02::1 Link local Scope All Node Multicast Addresses
FF01::2 Node Local Scope All Routers Multicast Addresses
FF02::2 Link Local Scope All Routers Multicast Addresses
FF05::2 Site Local Scope All Routers Multicast Addresses