Redundancy and Failover Designs

High availability (HA) means designing a network so services stay up even when something fails. The core idea is removing single points of failure: any one component whose failure takes down the whole system. HA combines redundancy (spare components) with failover (automatic switching to the spare), keeping critical services running through outages.

A single point of failure (SPOF) is any element with no backup, one router, one power supply, one internet link, whose loss stops everything. Identifying SPOFs is the first step in HA design. For each critical component you ask, "if this dies, what happens?" Wherever the answer is "total outage," you add redundancy.