A website administrator is setting up a cluster of web servers and wants to ensure that if one server goes down, the system in place will route the traffic through the others. Which network appliance should the administrator use?

In the scenario described, the use of a load balancer is crucial for ensuring high availability and reliability of the web services being provided by the cluster of web servers. A load balancer effectively distributes incoming network traffic among multiple servers, optimizing resource utilization and maximizing uptime.

If one server in the cluster fails, the load balancer has the capability to detect this failure and reroute traffic to the operational servers. This automatic rerouting is vital, as it allows the web application to continue functioning without interruption from the user's perspective. The load balancer can also provide other benefits, such as improved performance through effective traffic distribution and the ability to scale up by adding more servers to handle increased load.

While firewalls, routers, and NAT gateways serve important roles in network security and address translation, they do not provide the specific capability of distributing client requests among a cluster of servers. Firewalls focus on controlling access to network resources based on security policies, routers direct packets between different networks, and NAT gateways translate private IP addresses to a public IP address for Internet access, none of which inherently includes the traffic management features that a load balancer offers.