IPv6 Address Format Types & Compression Rules

IPv6 Address Format Types & Compression Rules

This article is a complete tutorial on IPv6 Address, Format, Types & Compression Rules. You will have the complete understanding of IPv6 after reading this.

Need of IPV6 in Networking

IPv6 is designed to be the successor of IPv4, but why? We explain briefly:

• The depletion of the IPv4 address space was the factor that motivated the migration to IPv6. 
• Projections indicate that the IPv4 addresses of the five RIRs between 2015 and 2020 will end.
• With a growing Internet population, a limited space of IPv4 addresses, problems with NAT and the Internet of things, it was time to start the transition to IPv6.
• IPv4 has a theoretical maximum of 4300 million addresses, plus private addresses in combination with NAT.
• IPv6 has a larger 128-bit address space, which provides 340 sextillion addresses.
• IPv6 resolves the limitations of IPv4 and includes additional improvements, such as ICMPv6.

There is no single date to transition to IPv6. In the near future, IPv4 and IPv6 will coexist. The transition is expected to take years. The IETF created various protocols and tools to help network administrators migrate networks to IPv6. Migration techniques can be divided into three categories:

1. Dual-stack : allows IPv4 and IPv6 to coexist on the same network. The devices execute IPv4 and IPv6 protocol stacks simultaneously.
2. Tunneling : is a method to transport an IPv6 packet in an IPv4 network. The IPv6 package is encapsulated within an IPV4 package.
3. Translation : Network address translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 package is translated into an IPv4 package and vice versa.

Representation of IPv6

IPv6 addresses are 128 bits long and are written as a string of hexadecimal values.

• The hexadecimal system is a sixteen base system.
• The base numbering system 16 uses the numbers from 0 to 9 and the letters from A to F.
• Four bits (half byte) can be represented with a single hexadecimal value.

IPv6 Address Rules

The writing format of an IPv6 address must take into account the following rules:

1. Rule 1: skip the initial 0

The first rule that reduces IPv6 address notation is that any initial 0 (zero) can be omitted in any 16-bit section or hex.

• 01AB can be represented as 1AB.
• 09F0 can be represented as 9F0.
• 0A00 can be represented as A00.
• 00AB can be represented as AB.

  2. Rule 2: Skip segments containing only zeros

• The two double dots (: :) can replace any single, contiguous string of one or more 16-bit segments (hextets) that are composed of only zeros.

Example: FE80: 0: 0: 0: 2AA: FF: FE9A: 4CA3 can be reduced to FE80 :: 2AA: FF: FE9A: 4CA3
Note: The double colon (: :) can only be used once in one direction; otherwise, the address will be ambiguous.

When both rules are used, this is usually known as a compressed format .

IPV6 Prefix Length:

IPv6 does not use dotted subnet mask dotted notation. The prefix length indicates the network portion of an IPv6 address using the following format:

• IPv6 Address / IPv6 Prefix Length
• The prefix length can range from 0 to 128.
• The typical prefix length is / 64.

IPv6 Address Types

There are 3 types of IPv6 addresses:

UNICAST IPv6 Address

An IPv6 unicast address uniquely identifies an interface of an IPv6-enabled device. A packet that is sent to a unicast address is received by the interface assigned to that address. As with IPv4, the source IPv6 addresses must be unicast addresses. The destination IPv6 addresses can be unicast or multicast addresses. The most common types of unicast IPv6 addresses are the global unicast (GUA) and link-local addresses.

• Global Unicast IPV6
• Similar to public IPv4 addresses.
• They can be statically configured or dynamically assigned.
• Currently, only global unicast addresses are assigned with the first three bits of 001 or 2000 :: / 3
• link-local addresses
• Allows a device to communicate with other devices with IPv6 enabled on the same link.
• Limited to a single link: cannot be routed beyond the link.
• If it is not configured manually in an interface, it will be created automatically.
• Every network interface with IPv6 enabled must have a link-local address.
• The link-local addresses are in the range of FE80 :: / 10 and can be set dynamically (SLAAC) or as static link-local addresses.
• LoopBack
• Used by hosts to send packets to themselves; cannot be assigned to a physical interface.
• Pinging the IPv6 loopback address allows you to test the TCP / IP configuration on the local host.
• Formed by all zeros, except the last bit, represented as :: 1/128 or simply :: 1.
• Unspecified addresses 
• The address formed by all zeros is represented as :: / 128 or simply ::
• It cannot be assigned to an interface and is only used as the source address.
• Unspecified addresses are used as source addresses when the device does not yet have a permanent IPv6 address or when the source of the packet is irrelevant to the destination.
• Unique Local Ipv6 Address
• They are used for local addressing within a site or between a limited number of sites. These addresses should not be able to be routed in the global IPv6, and should not be translated into global IPv6 addresses. Unique local addresses are in the range of FC00 :: / 7 to FDFF :: / 7.

Multicast IPv6 Address:

Multicast IPv6 addresses are used to send a single IPv6 packet to several destinations and have the prefix FFxx :: / 8. Multicast addresses can only be destination addresses and not source addresses. Two common groups of IPv6 multicast addresses assigned include the following:

1. Multicast Group of all Nodes FF02::1:
• All devices with IPv6 enabled are incorporated.
• It has the same effect as the broadcast IPv4 address.
2. Multicast Group of all FF02::2 Routers
• All IPv6 routers are incorporated.
• A router becomes a member of this group when it is enabled as an IPv6 router using the global ipv6 unicast-routing configuration command.
• The packets that are sent to this group are received and processed by all IPv6 routers on the link or on the network.

PROXIMITY DIFFUSION

An IPv6 proximity broadcast address is any unicast IPv6 address that can be assigned to several devices.

Note: IPv6 has no broadcast addresses.