IPv6 Part 1 -Address Representation-

calendar Apr 23, 2022 · 2 min read · IPv6  ·
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Overview


With the spread of the Internet, IPv4 address shortages have become a growing concern.The subordinate organizations in charge of each region of IANA, which manages the entire IPv4 address space, are returning and reallocating IPv4 addresses due to contract cancellations and other reasons, but these addresses are expected to run out in the future.
IPv6 addresses were created more than 20 years ago to address the exhaustion of IPv4 addresses.IPv6 does not seem to be very popular, but NTT docomo in Japan recently "launched IPv6 single stack method".

This article describes IPv6, which is gradually becoming more widely used.




Address Representation

IPv6 addresses are represented based on the following rules.

  • IPv6 address length is 128 bits (IPv4 address length is 32 bits).
  • One block consists of 16 bits and is expressed in hexadecimal (IPv4 is 8 bits per block and is expressed in decimal).
  • Separate blocks with : (colon) (IPv4 is separated with . (period).
  • Use lowercase letters for a through f.

Omitted Representation

The representation of IPv6 addresses can be partially omitted. It is recommended that omitted representation be used based on the following rules.

  • Omit the leading (consecutive) "0" in each block.
  • "0000" is omitted to "0".
  • If a "0000" block occurs in succession, it can be omitted for one time only to "::".
  • Use "::" to omit as much as possible.
  • If there is only one "0000" block, "::" must not be used ("0").
  • If there are multiple blocks that can be omitted using "::", omit the block with the most blocks that can be omitted.
  • If there are an equal number of blocks that can be omitted, omit the forward.

For example, the address shown earlier can be expressed as follows.

  1. Omit the leading "0" in the second block.
  2. Omit consecutive "0" in blocks 3 and 4; omit "0" in blocks 6 and 7.
  3. Finally, the following address representations are used.

Representation of Network ID

Like IPv4 addresses, IPv6 addresses are divided into < Network ID > and < Host ID >.In IPv6, Network ID is called Network Prefix and Host ID is called Interface ID. To indicate the network prefix length, use the format < IP address >/< prefix length >.

Example of node address:


Example of network prefix:


Reference


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