Which of the following would be used on a network to ensure access to resources if a critical host becomes unavailable?

QoS (Quality of Service) manages traffic prioritization and bandwidth allocation, and provides no failover or host redundancy capability.

CARP allows multiple hosts to share a virtual IP address, with one acting as master and others as backups. If the master fails, a backup host automatically assumes the virtual IP, ensuring that network resources remain accessible without manual intervention or reconfiguration of clients.

A VLAN segments a network into logical broadcast domains for traffic separation and security, but does not provide host-level redundancy or failover.

A DHCP server dynamically assigns IP addresses to clients and has no mechanism for ensuring continued access to a specific host or resource if that host fails.