IPv6 addresses are 128 bit long and provide an address space of 2^128 addresses.

IPv6 addresses are separated into eight blocks of four hexadecimal digits each. Blocks are separated by colons. Leading zeros can be shortened.

  • 2001:0DB8:3FA9:0000:0000:0000:00D3:9C5A
  • 2001:0DB8:3FA9:0:0:0:D3:9C5A
  • 2001:DB8:3FA9::D3:9C5A

IPv6 addresses also use network prefixes, which are specified in slash notation. The prefix is used to specify routes or address ranges, not a network ID. Routing table entry for IPv6

  • 2001:DB8:3FA9::/48

IPv6 addresses are automatically assigned by neighboring routers or DHCPv6 servers. Also, computers assign themselves a connection local address that is used only around local subnet


  • All local unicast addresses begin with fe80, i.e. the first 10 bits represent the format prefix, then 54 bits with zeros and then the interface ID.
  • cope of validity is the local connection
  • necessary for neighbour determination, always automatically configured

Structure of IPv6 addresses compared to IPv4 addresses





used Character

0-9, a-f


basic structure

8 16bit groups with 4 digits each, separated by ":"

4 octets (8bit) with 3 digits each, separated by "."

Number of possible addresses

approx. 340,28 sextile ions

approx. 4.29 billion

Comparison of typical IPv4 and IPv6 addresses

Address type



Special addresses:

unspezifizierte Adresse

0:0:0:0:0:0:0:0 bzw.
           ::           /128

localhost, loopback

0:0:0:0:0:0:0:0 bzw.
           ::1         /128

link-local unicast = APIPA

fe80::  …… /10 /16

global Unicast (öffentl.)

2001: …… (for providers)

site-local Unicast, private

Unique Local Adresses

fec0: …… -> replacements

fc00: …… /7 /8 /12 /16

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