IPv6 Concepts

• IPv6 always uses link-local addressing for communicating on a local network.
• When a device in a network fails to obtain an IP address from the DHCP server, it automatically assigns itself an IP address from the APIPA range (169.254.0.0/16). This usually indicates an issue with network connectivity

IPv6 Addresses

• IPv6 moves from 32 bits to 128 bits.

IPv6 Address Notation

The 32-bit IPv4 address are using four octets. IPv6 has 128 bits, so octets are gone. IPv6 addresses are written like this: 2001:0db8:0000:0000:0800:200c:00cf:1234 the : are quartet or hextet.

• First 64-bit → Network Prefix ( Routing prefix + Subnet ID )

• Second 64-bit → interface ID

• It has shorted notation you can remove zeros so 00cf becomes cf

  • Example: 2001:db8:0:0:800:200c:cf:1234
  • Result: 2001:db8::800:200c:cf:1234

• Example of using double colons: fe80:0000:0000:0000:00cf:0000:ba98:1234

  • Result: fe80::cf:0:ba98:1234 (only one :: allowed per address)

• IPv6 uses the /x prefix length naming convention to specify the number of bits in the network ID : fe80::cf:0:ba98:1234/64 The network prefix is 64 bits.

  • The address starts with fe80 followed by some number of hextets of all zeroes: 0000. fe80:0000:0000:0000

• IPv6 loopback address: ::1 without using double-colons 0000:0000:0000:0000:0000:0000:0000:0001

Link-Local Address

A host no longer has a single IP address unless the network isn’t connected to a router when a computer boots up it gives itself a link-local address.

• The first 64 bits of a link-local address are always fe80::/10 followed by 54 zero bits. fe80:0000:0000:0000
• The second 64 bits of a link-local address, the interface ID, are generated in two ways
• A system’s IPv6 link-local address is a unicast address: a unique address exclusive to that system.

Global Unicast Address+

A global unicast address is a fully routable public address that supports two-way connectivity between a device and the world.

Regional Internet Registries