Redundancy
Duplicating critical components or links so a backup takes over if the primary fails.
Redundancy is the practice of duplicating network components — links, power supplies, switches, or entire paths — so that no single failure brings down connectivity or services. On N10-009 it spans physical hardware (dual power supplies, bonded uplinks) and logical protocols. First Hop Redundancy Protocols such as HSRP, VRRP, and GLBP keep the default gateway available when a router fails, electing a standby device to assume a virtual IP and MAC address. The key exam distinction is that redundancy provides the spare capacity, while high availability is the measured outcome (uptime percentage). Redundant links still yield poor uptime if failover is slow, so the two work together rather than being interchangeable.
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