keepalived can be used to switch one or more IPs between one or more server systems. Typically, the underlying protocol for this is VRRP (Virtual Router Redundancy Protocol).

To determine whether localhost is currently in an active (ACTIVE), passive (BACKUP), or dysfunctional (FAULT) state within the server cluster, there are multiple approaches, each with its own pros and cons.

The goal is to provide a brief overview and examine some methods in detail, making it easier for other system administrators facing the same task.

TLDR: See “Part 5 – DBus”