N10-009 Question 222
Single answerHigh-availability approaches: Active-active, Active-passiveA company runs a customer-facing web application behind two load balancers in an active-active design. During a maintenance window, one load balancer is taken offline, and users continue accessing the application with only a slight increase in response time. Later, the company considers replacing this design with an active-passive pair to simplify management. Which statement best describes the trade-off the network administrator should expect if the company moves to an active-passive high-availability approach?
- A
The passive device will share traffic with the active device during normal operation, so performance should remain about the same.
- B
The passive device will stay idle until a failure occurs, which simplifies failover behavior but does not use both devices for load sharing during normal operation.
- C
Active-passive requires both devices to process every session simultaneously, which improves redundancy but increases the chance of asymmetric routing.
- D
Active-passive eliminates the need for health checks because the backup device can detect failures only after clients report outages.
Show answer and explanation
Correct answer: B
Explanation
The key distinction is that active-active uses multiple devices simultaneously for production traffic, improving utilization and often increasing available capacity, while active-passive keeps one device in reserve until a failure occurs. In the scenario, the active-active pair allowed continued service during maintenance with only reduced capacity, which is typical when one participating device is removed. Moving to active-passive can simplify operations and failover logic, but the standby device is usually not contributing to traffic handling during normal operation. This trade-off is consistent with common vendor HA documentation and Network+ objectives: active-active focuses on load sharing plus redundancy, while active-passive focuses on redundancy with simpler operational behavior. Best practices still require monitoring and health detection mechanisms such as heartbeat links, interface monitoring, and service checks so failover can occur quickly and predictably.
- A. Incorrect.
Incorrect. This describes active-active behavior, not active-passive. In an active-active design, both devices typically handle production traffic at the same time, which can improve resource utilization and throughput. In an active-passive design, the standby unit is generally not forwarding normal production traffic until failover occurs.
- B. Correct.
Correct. In an active-passive high-availability design, one device actively handles traffic while the standby device waits to take over if the active unit fails. This often makes the design easier to understand and troubleshoot, but it means the organization is not using both devices to distribute production traffic under normal conditions. As a result, there may be less efficient hardware utilization compared with active-active.
- C. Incorrect.
Incorrect. Active-passive does not normally require both devices to process every session at the same time. Some implementations synchronize state information for faster failover, but the standby unit is not usually forwarding live traffic concurrently. This option confuses session/state synchronization with simultaneous traffic processing.
- D. Incorrect.
Incorrect. Health checks are a core part of high-availability designs, including active-passive. Heartbeats, keepalives, link monitoring, and service health checks are commonly used so the standby device can detect failure conditions quickly and take over. Relying on client complaints would not meet normal HA best practices.