Explanation
An out-of-band (OOB) solution is a method of accessing and managing a server remotely without using the network connection or the operating system of the server. An OOB solution can use a dedicated management port, a serial console, or a KVM switch to provide a resilient connection while performing changes to the network configuration of the server. An OOB solution is more reliable than a VNC or RDP console, which depend on the network and the operating system, and more convenient than a crash cart, which requires physical access to the server.
References: CompTIA Server+ SK0-005 Certification Study Guide, Chapter 2, Lesson 2.3, Objective 2.3