What is IPv5

IPv6 - Internet Protocol Version 6

As Internet Protocol (Version 6), IPv6 is responsible for the switching of data packets through a packet-switching network, the addressing of network nodes and stations, and the forwarding of data packets between subnetworks. With these tasks, IPv6 is assigned to layer 3 of the OSI layer model.
The main task of the Internet Protocol is to transfer data packets from one system to another system via various networks (routing).

IPv6 is the direct successor to IPv4 and part of the TCP / IP protocol family. IPv6 has been available since December 1998 and was specified primarily because of the address shortage and various shortcomings of IPv4. Since more and more people, machines and devices around the world are to be connected to the Internet with a unique address, the 4 billion IPv4 addresses are no longer sufficient.

Why IPv6?

IPv6 is considered to be the silver bullet against so many problems with network protocols and at the same time it is condemned as the devil's stuff that causes new unknown problems. The fact is that administrators, programmers and manufacturers have to relearn IPv6. Many recipes from the IPv4 world are no longer suitable for IPv6. To make matters worse, everyone involved lacks experience with IPv6. There aren't that many IPv6 gurus to consult with a big problem.

With IPv6, the end-to-end principle is consistently thought ahead. An interface can have several IPv6 addresses and there are special IPv6 addresses to which several interfaces are assigned.
IPv6 not only solves the shortage of addresses, it also makes configuration and operation easier. Stateless IPv6 configuration and link-local addresses, available after the computer is started, simplify the setup and operation of a local network.
In order for this to be successful, planners and installers of IP networks are required to adopt a new way of thinking.

Internet Protocol Version 5 (IPv5)?

IPv5 was officially called ST-2 (Internet Stream Protocol Version 2) and was an experimental protocol for real-time data streams. ST-2 was originally intended to multicast audio and video. This should bring the bandwidth reservation advantages of ATM into the IP networks. It was not enough for series production. That is why there was no IPv5 in practical use. And ST-2 has been replaced by RSVP (Resource Reservation Protocol) for bandwidth requirements on routers.

Parallel operation of IPv4 and IPv6 (dual stack)

IPv4 no longer has a future and a swift change to IPv6 appears necessary. At the same time, not only must IPv6 be introduced, but IPv4 must also be operated in parallel. This operating state is called "dual stack".
Both protocols must be operated until all computers in the world are capable of IPv6. And that can take time. There are many network components that do not support IPv6 and must first be replaced with IPv6-capable components. On the other hand, the market for IPv6 is not yet big enough that the development of IPv4-comparable products with IPv6 is worthwhile.
But there is ultimately no getting around IPv6. Otherwise you run the risk of missing out on technical developments.

Benefits of IPv6

For many, IPv6 is just an IPv4 with longer addresses. But this view is completely wrong. IPv6 is a protocol with many new features. The experiences that someone brings with them from the IPv4 world can only be transferred to IPv6 to a limited extent.

  • longer addresses and therefore a larger address space
  • multiple IPv6 addresses per host with different scopes
  • Autoconfiguration of the IPv6 addresses possible
  • Multicast through special addresses
  • faster routing
  • Point-to-point encryption with IPsec
  • Quality of Service
  • Data packages up to 4 GByte (jumbograms)

Overview: IPv6

IPv6 addresses and address space

An IPv6 address consists of 128 bits. This address length allows an unimaginable amount of 2 to the power of 128 or 3.4 x 10 to the power of 38 addresses. This means that IPv6 addresses have enough space to map as many network topologies as possible. At the same time, it is also about simplifying routing.

Because of the unwieldy length, the 128 bits of the IPv6 address are divided into 8 blocks of 16 bits each. 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 in the blocks can be omitted. A sequence of 8 or more zeros can be replaced once 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. This is the modified EUI-64 format.
In this way, the interface can be clearly identified regardless of the network prefix.

The network mask or subnet mask known from IPv4 is no longer available. A prefix is ​​used to identify the address range or the subnet, which can be added to the address with a "/" if necessary.
As a rule, the first 64 bits of an IPv6 address stand for the network and the remaining 64 bits for the host. This means that the prefix length is usually always "/ 64". However, this rule does not apply in every network.

An IPv6 host not only has one IPv6 address, but usually three IPv6 addresses. A link-local address, a global address, and a temporary address. Each of these addresses has a different scope. The link-local address is only valid in the local network. It is created without manual configuration. This means that connections in the local network are always possible. The link-local address is also required to get a global IPv6 address so that connections to the public network are possible.

IPv6 autoconfiguration (SLAAC / DHCPv6)

IPv6 enables complete auto-configuration by a host with an IPv6 address, standard gateway and DNS server. It should be noted that an IPv6 host usually has several IPv6 addresses and can get these and all other parameters for a complete auto-configuration in different ways. Manual, i.e. static, IPv6 configuration is of course also possible.

A distinction is made between a "stateless" and a "stateful" autoconfiguration. With "stateless" the IPv6 host generates its own IP address. With "stateful" it is assigned it centrally. In contrast to IPv4, the IPv6 configuration does not have to be assigned centrally in the local network. Setting up an IP network is therefore much easier under IPv6.
Thanks to the IPv6 auto-configuration, communication in the local network should always be possible.

Privacy Extensions

The MAC address of the network interface is typically used for the interface identifier of the IPv6 address. Since MAC addresses are unique worldwide, a globally unique interface identifier is created.
Privacy extensions have been introduced to allay concerns about data protection and privacy. Privacy extensions regularly generate a random interface identifier that does not allow any conclusions to be drawn about the MAC address and thus the host.

Address selection

Address selection is a process that decides which IP address is used. If a host has both an IPv4 and an IPv6 address (dual stack), which one does it use? And if a host uses an IPv6 address, which one? The link-local, the global or a temporary IPv6 address?


IPv6 combines network nodes, routers, time servers and other services or service providers in multicast groups. Each group can be reached via its own address. This means that you can address a central service in a local network without knowing the IPv6 address of the host. Any host can feel assigned to a multicast group and process packets to a multicast address.

NDP and ICMPv6

Neighbor Discovery Protocol, or NDP for short, is the IPv6 protocol for exchanging link-local relevant messages such as router discovery and neighbor discovery. The NDP messages are transmitted with ICMPv6.

IPv6 headers and extension headers

Each IPv6 data packet consists of a header and the payload (user data). The header precedes the user data. The IPv6 header contains, among other things, the IP address of the sender and recipient and other information that is important for IP routing and is evaluated by the routers on the way from the source to the destination.
The IPv6 header has a fixed length of 40 bytes. Optional information is stored in the extension header.


IPsec is an extension of the Internet Protocol (IP) to include encryption and authentication mechanisms. This gives the Internet Protocol the ability to transport IP packets cryptographically secured over public and insecure networks.
IPsec was developed by the Internet Engineering Task Force (IETF) as a component of IPv6 and later also specified for IPv4.


An interface connected to a local network is considered "multihomed" if it has several global IPv6 addresses with different prefixes. This means that the local network is connected to the Internet via several ISPs. The interfaces have addresses from each participating ISP. This is not just for redundancy. The network used for the transmission can also be determined by selecting the sender address.


The mechanisms for "stateless" autoconfiguration allow the addition and removal of global prefixes and thus the reconfiguration of a network during operation.
Thanks to renumbering, an interface can be populated with new addresses relatively easily. Be it to introduce a new address scheme or to change the provider. An interface is brought into a multihomed-like state. At the same time the validity of the old addresses is slowly being phased out.
Several network access routers can be configured differently for this purpose. Via router advertisements, one can tell the hosts "prioritize me" and another router "don't use me". In this way you can put a new router into operation and take another one out of operation. Small SoHo routers can't do that, of course.

Flow labels

Flow labels are markings for IP packets, based on which routers or packet filters can handle packets differently. The criteria according to which a flow label is awarded must be determined on a case-by-case basis. Ideally, all packages with the same flow label should also be treated in the same way.
Flow labels do not replace MPLS and there is a separate field for QoS. Whether it will play a role in the future remains to be seen.

Mobile IPv6

Mobile IPv6 allows migrating between different networks without losing the connection on the IP level. It's about communicating without interruption, even if you change the network and thus the prefix. It is a kind of handover at the IP level.


The user data length is noted in the header, but the corresponding field cannot accept any values ​​beyond 65,535. With the jumbo payload option in the associated extension header, user data of just under 4 gigabytes are also possible. However, this assumes that Path MTU packets of this size are permitted. There is no point in defining large packet lengths if the routers to be transmitted report an error as a result. Jumbograms are therefore only useful for special applications and, under certain circumstances, only in local networks.

Transition procedure from IPv4 to IPv6

The practical implementation of IPv4 to IPv6 is a problem because it is impossible to make all network devices IPv6-capable at once. So that the change is easier and investments in old IPv4 technology do not become obsolete, there are various procedures that are intended to facilitate the transition from IPv4 to IPv6.

Migration to IPv6: yes or no?

Let's be honest. IPv6 is not hype like other commercially driven IT topics. The introduction of IPv6 is an infrastructure measure that initially offers few advantages, means additional work and is usually associated with additional costs.

For normal users, not much changes at first, which is why IPv6 is not user-driven either. IPv6 only becomes exciting for normal users when there are sensible applications to access devices at home while on the move. That is not really possible right now.
For large networks, IPv6 is a redemption. Especially where even the large private 10/8 network is used multiple times because the company's internal structures cannot be mapped with a single 10/8 network.

There is no reason not to use IPv6. Paranoid administrators who want to keep every bit under control and see it as their job to maintain Excel sheets with IP addresses are often an obstacle. But none of that works. There is no practicable way to manage IPv6 addresses for all possible devices in a meaningful way. That is not even necessary.

Those who do not offer IPv6 have to expect that at some point they will suddenly be left behind by their customers. And then the question is, by when will IPv6 be implemented in a stable manner.
That is why you should implement IPv6 as long as you can still afford problems (to be corrected) in the implementation, because IPv4 is still available as a functioning fallback. Once IPv6 is absolutely necessary, you can no longer afford to make mistakes when converting. And what change in IT is already going without errors?

Tasks and exercises with the Raspberry Pi

Overview: IPv6

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Collection: IPv6

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