What is a floating IP?

The internet – plainly put – consists of many computers connected by cables, fibre optic cables, and wireless receivers. They exchange data based on a common ‘language'. This common standard is known as the Internet Protocol (IP). Data is arranged in such a way that computers, which understand the common protocol, can interpret it. An IP address, also referred to as an 'IP', makes digital devices detectable in a network. It is a crucial prerequisite so that electronic data packets can be delivered reliably. The devices communicate with one another, for example, over the internet. The IP address ensures that data from the sender reaches the correct recipient – for example, from a web browser to a web server or vice versa. An IP address can be assigned to both single and multiple devices at the same time. Likewise, a single device can have multiple IP addresses at the same time. However, in order to be able to understand exactly what a floating IP is, you first need to know the difference between dynamic and static IP addresses.

When a computer connects to the internet, in most cases the Internet Service Provider (ISP) assigns a dynamic IP address to it. Dynamic IP addresses are the most cost-effective standard for users and providers. They are characterised by the fact that they are only assigned temporarily and change after a certain time, which is either fixed (e.g. for 24 hours), or is irregular. The user then receives a new dynamic IP address for their computer from the respective internet service provider and the previous address will then be signed to a different user.

A static IP, on the other hand, is a fixed address and is permanently assigned to a device. Static IP addresses are found mainly in the web server or e-mail server area, or wherever offers or website content must be accessible via a fixed URL , so that users or processes can (re)find them without any problems. Computers in a network or peripheral devices (such as printers) have fixed IPs, so that the individual devices within the network can easily communicate with one another.

So that users don’t have to remember complex numbers, it’s possible to assign a domain name to a static IP address e.g. www.example.org. The numerical IP, the 'connection number' of a device in the network, is therefore translated into a name that can easily be remembered. This is generally only reserved for static IPs. It doesn’t make much sense for dynamic IPs since the user changes so frequently.

A floating IP is usually a public, routable IP address that is not automatically assigned to an entity. Instead, a project owner assigns them to one or more entities temporarily. The respective entity has an automatically assigned, static IP for communication between instances in a private, non-routable network area, as well as via a manually assigned floating IP. This makes the entity’s services outside a cloud or network recognisable and therefore achievable.

In appropriately configured failover scenarios, an IP 'floats' to another active unit in the network so that it can take on the function of a dormant entity without a time delay, and can then answer incoming requests.

Users obtain floating IPs for their projects from different pools that the system administrator configures and provides as server resources. As soon as a user receives a floating IP, they become the 'owner'. They can assign it to an entity, remove it, and then assign it to another at any time. Even if an entity is terminated, the user does not 'lose' the associated floating IP. It remains as a resource and can still be assigned to another entity when needed.

A major reason for using several parallel floating IP pools is that each pool can be operated by another internet service provider or can also be assigned by other external networks. This ensures that the connectivity or availability is maintainable even if an internet service provider should fail due to a malfunction.

Maximum availability is one of the key factors in every production environment. In the communication network, however, a single error can cause applications to fail. Developers do sleep better knowing that their applications are designed to withstand any conceivable error scenarios. The goal is to provide a highly available piece of infrastructure with minimal downtime.

A floating IP can serve as a flexible load balancing address, helping to balance peak loads by distributing incoming network traffic to different network nodes. Network nodes are devices which connect two (or more) transmission paths of a telecommunication network. As with a computer that distributes workflows across multiple processors, load balancing also handles large amounts of simultaneous requests or more complex calculations by splitting the load across multiple parallel systems.

If a primary load balancer or a central application server in a cluster fails on one side, a floating IP can be immediately assigned a redundant application server or a secondary load balancer in a correspondingly configured system. The IP 'floats' to the active unit, which immediately carries out the desired processes. An unplanned change between network services is referred to as 'failover'. This kind of protection is especially recommended for critical applications.

A planned change from a primary to a secondary system is referred to as a 'switchover'. The targeted transmission of services is not triggered by errors, but is usually controlled by a system administrator. A classic reason for a switchover is, for example, routine maintenance of the primary or secondary systems where a parallel instance temporarily takes over its function.

One of the main advantages of floating IPs is their flexibility – the free and needs-oriented assignability. Floating IPs are therefore suitable for use in both failover and switchover environments – for example, for performing upgrades of applications or entire sites with minimal downtime. While an upgrade is applied to one entity, another one takes on the traffic. Once the upgrade has been successfully completed, the traffic is redirected to the updated unit.

Another advantage: even if several or even many different entities are concealed behind a service being offered, the floating IP appears on the surface to users (who make use of the service) rather than the server’s IP that offers the respective service.