What is the highest IPv6 address

IPv6 addresses

An IPv6 address is a network address that logically addresses a host uniquely within an IPv6 network. The address is required at the IP or switching level (of the OSI layer model) in order to be able to send and deliver data packets. In contrast to other addresses, an IPv6 host has multiple IPv6 addresses that have different ranges of validity.
Specifically, this means that when you talk about IPv6 addresses, it is not always clear which range of validity these IPv6 addresses have. A rough distinction is made between link-local and global IPv6 addresses. The link-local IPv6 address is only valid in the local network and is not routed. The global IPv6 address is valid beyond the local network in the Internet.

An IPv6 address is 128 bits long. This address length allows an unimaginable amount of 2128 or 3.4 x 1038 IPv6 addresses. That is 340,282,366,900,000,000,000,000,000,000,000,000 IPv6 addresses, i.e. around 340 sextillion addresses. With IPv4 one speaks of around 4.3 billion addresses.
The address space of IPv6 is sufficient to pave the equivalent of every square millimeter of the earth's surface, including the oceans, with around 600 quadrillion addresses. Compared to IPv4, the allocation and allocation of IPv6 addresses is therefore very generous.

Types of IPv6 Addresses

  • Unicast: addresses for a single interface.
  • Anycast: Addresses for several interfaces, only one of which receives the packet.
  • Multicast: Addresses for several interfaces that all receive the same packet.
  • Broadcast: do not exist and are implemented with multicast addresses.


One of the reasons for switching from IPv4 to IPv6 is the larger address range of IPv6. But why the same 128-bit address width? The reason is that the IP addresses should be long enough to be able to generously segment or divide the entire address space. As far as possible, all network topologies should be able to be taken into account. At the same time, the routing should be simplified.

In order for routers to work efficiently, addresses must be assigned in a hierarchically structured manner. The IP address must be long enough so that all levels of the hierarchy can be mapped. It would be desirable if there was enough room left for future developments. Therefore, when segmenting IPv6 addresses, a relatively large amount of waste is accepted.

IPv6 address in detail

An IPv6 address consists of 128 bits. Because of the unwieldy length, the 128 bits are divided into 8 by 16 bits. Each 4 bits are represented as a hexadecimal number. 4 hex numbers are grouped and separated by a colon (":"). To simplify the notation, leading zeros are left out of the blocks. A sequence of 8 zeros can be replaced by two colons ("::").

An IPv6 address consists of two parts. The network prefix (prefix or network ID) and the interface identifier (suffix, IID or EUI).
The network prefix identifies the network, subnet or address range. The interface identifier identifies a host in this network. It is formed from the 48-bit MAC address of the interface and converted into a 64-bit address. It is the modified EUI-64 format.
In this way, the interface can be clearly identified regardless of the network prefix.

Segmentation: prefix and prefix length

The network mask or subnet mask known from IPv4 is no longer used with IPv6. In order to still be able to segment and subdivide address areas or subnets, the prefix length is defined and appended to the actual IPv6 address with a "/" (slash). The hierarchical structure of the prefix is ​​intended to simplify routing with IPv6.
By default, "/ 64" is the prefix length. However, there are other typical prefixes that are 32, 48, and 56 bits long. This has something to do with the assignment of prefixes. If you want to operate your own networks, you get a shorter prefix than / 64 from your provider and thus get more address space.

This means that every network, no matter how small, is assigned at least one subnet. In this subnet, gigantic 264, so over 18 trillion individual addresses can be assigned. This means that users can save themselves the use of private IP addresses and procedures such as NAT. The abundance of addresses in IPv6 makes it possible.

With IPv6, old burdens in the network division can be eliminated and, thanks to the large address space, the IPv6 address plan can be generously redesigned. Since each host can have multiple IPv6 addresses, it is conceivable that each service or application on a server could have its own IPv6 address. A service can then switch to any other hardware within the same subnet without having to change the IPv6 address of the service.

Note: The IPv6 autoconfiguration does not work with less than 64 bits in the interface identifier. Of course, that doesn't mean that someone isn't trying. But then there are problems with generating the global IPv6 address, for example, because this mechanism assumes that it is allowed to assign 64 bits itself. If the mechanisms of the auto-configuration no longer work, you have to configure IPv6 addresses manually or assign them via DHCPv6. Experience has shown that it is not a good idea to experiment with it.

Address assignment by IPv6 provider (assignment of the prefix)

The original plan for dividing up the address space was that every customer should have a /48 network. It was quickly recognized that this is too generous and therefore switched to longer prefixes. Either / 56 or / 64. / 56 should be normal because you have to assume that a customer operates several networks. Possibly also in the home area. Small companies in particular then have more leeway without having to accept restrictions.
Enterprise customers who operate their own networks usually receive / 48 networks from their provider. Large network operators and providers are generally assigned /32 networks. Larger network operators also get larger networks.

IPv6 address scopes (ranges of validity)

IPv6 differs from IPv4 not only in terms of longer addresses, but also in the areas of validity (address scopes) for these addresses. This means that every IPv6 address has a so-called scope. The scope is that part of a network in which the associated address is recognized as valid and routed.

While IPv4 only differentiates between private and public addresses, IPv6 addresses can be more complex.

  • Host scope
  • Link-local scope
  • Unique local scope
  • Site-Local-Scope (obsolete)
  • Global scope
  • Multicast scope

The two most important scopes are the link-local scope and the global scope. Only IPv6 packets with a global sender address are routed outside the local network.

Privacy Extensions (RFC 4941)

Because a global IPv6 address raises concerns about data protection and privacy because of the unique interface identifier, "Privacy Extensions" were introduced to allay those concerns. That is why privacy extensions are activated by default. If privacy extensions are activated, each interface receives at least one additional temporary global IPv6 address, the interface identifier of which is generated randomly and changes regularly. The random interface identifier then no longer allows any conclusions to be drawn about the host.
Temporary global IPv6 addresses are only valid for a limited time. If privacy extensions are active, an IPv6 address is no longer suitable for identifying a specific host.

Tasks and exercises with the Raspberry Pi

If you want to experiment with IPv6, you can do it on a Raspberry Pi, for example. There are also a few tasks and exercises specifically for IPv6.

Overview: IPv6

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A PDF file of all articles on Internet Protocol Version 6 from this website. The compilation takes into account the introduction to the basics of IPv6 with detailed descriptions and numerous tables and figures. Learn more about the possibilities and relationships in the IPv6 network.

More information and to download