F5 F5CAB4 Practice Test Questions Answers

BIG-IP provides two supported and documented methods to manually force a device into standby state in a high-availability (HA) configuration:

CLI method (A):

tmsh run /sys failover device standby

This is the correct and supported TMSH command to force the local device to transition from active to standby.

Configuration Utility method (B):Navigating to Device Management > Devices > Local Device (Self) and selecting Force to Standby performs the same operation through the GUI and is fully supported.

Why the other options are incorrect:

C is incorrect: Traffic Groups do not provide a “Force to Standby” option for the local device; traffic groups are used to manage which device owns specific traffic, not to force device-level failover.

D is incorrect: tmsh run /sys failover standby is not a valid TMSH command. The correct syntax requires device standby.

Thus, the correct answers are A and B.

When BIG-IP is configured to use remote authentication (such as LDAP), all authentication and authorization attempts—including successes and failures—are logged to /var/log/secure.

For LDAP-based administrative login issues, /var/log/secure contains:

LDAP authentication failures

PAM authentication errors

Authorization and access-denied messages

Details explaining why a remote user could not log in

Why the other options are incorrect:

/var/log/user.log is not a standard BIG-IP log file for authentication.

/var/log/ltm logs traffic management events, not user authentication.

/var/log/messages contains general system messages but not detailed authentication failure information.

Therefore, the correct log file to troubleshoot LDAP administrative login failures is /var/log/secure.

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Managing how a BIG-IP communicates with external management services like Syslog is a core Control Plane task. The Configuration Utility organizes these settings under the "System" menu. Specifically, to define remote logging destinations and formats, the administrator must navigate to System > Logs > Configuration to ensure the Control Plane correctly forwards system events to external collectors

Reactivating a BIG-IP license is a traffic-disruptive operation. During the license reactivation process, the BIG-IP system performs a configuration reload, which results in a temporary interruption of all traffic processing. Because traffic handling is affected, F5 explicitly recommends scheduling license updates during a maintenance window.

This behavior is documented in F5 Knowledge Base articles, which state that license reactivation impacts traffic and must be planned accordingly during upgrades or system changes.

The other options are not considered disruptive:

Creating a QKView is primarily a diagnostic task and does not interrupt traffic.

Running tmsh save sys config only saves the running configuration to disk.

Generating a UCS is resource-intensive but does not reload configuration or interrupt traffic processing.

F5 Support uses a specific scale to categorize the urgency of technical issues, which helps the Control Plane management team prioritize resources effectively.

Severity 1 (Critical): Used for emergency situations where a production site is completely down, or there is a critical impact on business operations with no workaround available.

Severity 2 (High): Assigned when a system is severely degraded, or a primary function is significantly impacted, but the site remains operational in a degraded state.

Severity 3 (Medium): Applicable for issues where there is a partial loss of non-critical functionality, or the system is failing intermittently but the core business is not currently impacted.

Severity 4 (Low): This is the appropriate level for non-critical issues, general "how-to" questions, or maintenance planning. Since the administrator plans to resolve this issue in two weeks, it falls under the category of a low-priority maintenance task that does not require an immediate response from F5 support.