F5 BIG-IP Administration Control Plane Administration (F5CAB4) exam F5CAB4 Exam Dumps: Updated Questions & Answers (August 2026)

The recommended and supported method for creating BIG-IP users from the CLI is through TMSH , using the authentication subsystem.

tmsh create auth user < username > prompt-for-password:

Properly creates the user within BIG-IP’s AAA/authentication framework

Encrypts the password securely

Ensures the user is stored and managed correctly in the BIG-IP configuration database

Is fully supported and documented

Why the other options are incorrect:

B is unsafe and unsupported because editing bigip.conf directly and storing clear-text passwords violates security and configuration management best practices.

C (f5adduser / f5passwd) is deprecated and not recommended for modern BIG-IP versions.

D creates a Linux system user only , not a BIG-IP administrative user, and will not allow access to the Configuration Utility or TMSH roles.

On BIG-IP systems that participate in a Device Service Cluster (DSC), each device compares the remote device’s system time to its own system time. If the difference is outside the ConfigSync time threshold (commonly referenced as 3 seconds by default ), BIG-IP updates the shell prompt to show “Peer Time Out of Sync” , and ConfigSync operations may fail until time is corrected (typically by fixing NTP reachability/configuration, or in some cases adjusting the threshold). ( cdn.studio.f5.com )

This message is specifically about time drift between peers in the trust domain/DSC—not basic reachability (so B is not what it means), and it does not prove which side is “correct” (so C is too specific). It also doesn’t directly mean an NTP source is “skewed” (A can be a cause , but the prompt message itself indicates the peer-to-peer time mismatch condition). ( cdn.studio.f5.com )

Connectivity management requires a proper logical-to-physical mapping within the BIG-IP Control Plane.

VLAN Association : In TMOS, a Self IP address is not assigned directly to a physical interface. Instead, it is assigned to a VLAN (Virtual Local Area Network) object.

Procedural Troubleshooting : If a Self IP is unreachable, the primary failure point is often that the IP was associated with the wrong VLAN, or the VLAN itself is not correctly associated with the intended physical interface or trunk.

Layer 2 Mapping : The Control Plane requires the VLAN to be " up " and " untagged " or " tagged " on a valid interface for traffic to flow. If the administrator selects the incorrect VLAN, the Self IP will exist in the configuration but will be logically isolated from the physical network wire.

For an issue involving an HTTP virtual server, the first log file to check is /var/log/ltm . A BIG-IP virtual server is an LTM traffic-management object, and runtime events related to virtual servers, pools, pool members, monitors, availability changes, and traffic-management behavior are normally written to the LTM log. /var/log/httpd/httpd_errors is not the correct first choice because it relates to the BIG-IP Configuration Utility web service, not to an HTTP application virtual server processing client traffic. /var/log/audit records administrative configuration changes, such as who modified an object and when. /var/log/messages contains broader system-level messages but is not the primary LTM troubleshooting log. Therefore, when the problem statement specifically says an HTTP virtual server is having an issue, the control-plane troubleshooting path starts with /var/log/ltm .

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In a High Availability pair, the " Force to Standby " action is a Control Plane command used to trigger a manual failover. This option is only logical and available on the device that is currently in the Active state. If the button is greyed out, it indicates that the administrator is already logged into the Standby unit, which has no active traffic groups to relinquish.

When restoring a User Configuration Set (UCS) file, BIG-IP allows administrators to selectively exclude the license during the restore process. From the CLI , this is accomplished using the no-license option with the tmsh load /sys ucs command.

The command:

tmsh load /sys ucs < ucs filename > no-license

restores:

System configuration

Certificates and keys

Device and traffic objects

while explicitly excluding the license file , which is required when:

Migrating configurations between devices

Restoring to hardware with a different license

Avoiding license conflicts or overwrites

Why the other options are incorrect:

A does not provide the option to exclude the license.

B restores the UCS including the license , which does not meet the requirement.

D is incorrect because the BIG-IP GUI does not provide a checkbox to exclude the license during UCS restore.

Therefore, the correct and supported method is C .

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Comprehensive and Detailed Explanation From BIG-IP A34dministration Control Plane Administration documents: Authentication and authorization events are handled by the system ' s PAM (Pluggable Authentication Modules). For Control Plane security auditing, all login attempts—whether local or remote (LDAP/RADIUS/TACACS+)—and SSH-related security events are recorded in /var/log/secure. This is the primary log for troubleshooting administrative access issues

F5 architecture distinguishes between the Data Plane (TMM processing application traffic) and the Control Plane (Linux host processing management tasks). High Control Plane CPU utilization typically points to administrative activities such as heavy GUI usage, complex API calls (iControl), large-scale configuration synchronizations, or intensive logging/monitoring tasks rather than the actual switching or load balancing of application data.

Comprehensive and Detailed Explanation From BIG-IP Administration Con 10 trol Plane Administration documents: Placing a device in the FORCED_OFFLINE state is a critical procedural concept for HA maintenance 111213 . 1415 Unlike simply being ' Standby 16 ' , the FORCED_OFFLINE state ensures tha 17 t the Control Plane will not participate in failover selection, effectively preventing the device from becoming ' Active ' even if the peer fails 18 . This state also allows the administrator to terminate existing connections to ensure no traffic is being processed during the maintenance window 19 .

Traffic Groups are the mechanism BIG-IP uses to control which device owns specific application traffic in a high-availability (HA) configuration. When maintenance is required on a device that is currently active for a traffic group , the correct and recommended action is to fail over that traffic group to another device in the device group.

Failing over the traffic group moves ownership of that traffic group (and the virtual servers associated with it) to another available device without forcing the entire device into standby.

This allows targeted maintenance while minimizing impact to other traffic groups that may still be active on the device.

Why the other options are incorrect:

A is unnecessary and incorrect; traffic groups are not recreated for routine maintenance.

C forces the entire device to standby, which may move more traffic than intended.

D (Demote) affects device trust/priority behavior and is not the standard or recommended method for moving traffic group ownership.

Therefore, selecting the Traffic Group and choosing Failover is the correct solution.