F5 F5CAB4 - BIG-IP Administration Control Plane Administration (F5CAB4) exam

On BIG-IP systems, SSH access restrictions are configured under the /sys sshd object. The allow property defines the IP addresses or networks permitted to connect to the management interface using SSH .

The list command is used to display the current configuration settings.

Therefore, tmsh list /sys sshd allow correctly displays the configured allowed IP ranges.

Why the other options are incorrect:

A (show) displays runtime or statistical information, not configuration values.

C and D incorrectly reference /etc/hosts.allow; BIG-IP manages SSH access through TMSH objects, not by directly listing host files in this context.

In the BIG-IP Configuration Utility , all system backup and restore operations—including UCS (User Configuration Set) file restoration —are performed from the Archives section.

The correct navigation path is:

System > Archives

From this location, the administrator can:

Upload UCS files

Restore UCS backups

Manage system archive files used for backup and recovery

Why the other options are incorrect:

A. System > Configuration is used for general system settings, not backup restoration.

C. Local Traffic > Virtual Servers is used for application traffic objects.

D. Local Traffic > Policies manages traffic policies, not system backups.

Therefore, the correct section to restore a UCS file using the Configuration Utility is System > Archives .

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The Control Plane is responsible for ARP (Address Resolution Protocol) management for Virtual Addresses. For a Virtual Server to be reachable, the BIG-IP must respond to ARP requests for that IP. If the " ARP " setting is disabled on the Virtual Address properties, upstream routers cannot resolve the MAC address of the BIG-IP, leading to connectivity failure even if the service itself is " Available. "

When restoring a UCS file to replacement hardware (RMA device) , the license from the original device is not valid on the new system. If the UCS restore attempts to load the old license, BIG-IP reports license errors such as “License is not operational” , which can prevent traffic objects (including pools and virtual servers) from loading correctly.

To avoid this issue, F5 documentation recommends restoring the UCS without the license , using the following command:

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

This approach:

Restores all configuration objects (LTM, networking, certificates, keys, etc.)

Excludes the invalid license tied to the old hardware

Allows the administrator to activate a new license separately on the replacement device

Why the other options are incorrect:

A. Remove the license information from the UCS archive Not supported or recommended; UCS files should not be manually modified.

B. Revoke the license prior to restoring License revocation does not prevent the UCS from attempting to load license data.

D. Reactivate the license on the new device using the manual activation method This must be done after restoring the UCS and does not prevent the restore failure itself.

Therefore, the correct and supported method to avoid this error is C .

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In the BIG-IP Configuration Utility, status icons provide immediate health information. A red diamond specifically indicates that the object itself is administratively disabled . When a virtual server is disabled, BIG-IP will not accept or process traffic for that virtual server, regardless of pool or node state.

If all pool members were down , the virtual server would typically show a yellow triangle (available but no resources).

If all pool members were disabled , the virtual server would usually still be enabled but unavailable due to pool status, not shown as a red diamond.

Protocol mismatch (HTTPS sent to HTTP) does not change the administrative status icon of the virtual server.

Therefore, the red diamond clearly indicates the virtual server is disabled , making D the correct answer.

Maintaining an accurate and synchronized clock across all members of a device group is a fundamental requir5ement for the BIG-IP Control P6lane to establis7h and maintain device tru8st9.

Time Delta Impact : As shown in the exhibit, the " Time Delta to Local Device (sec) " is 12 .

Trust Mechanism : Device trust relies on secure certificate-based communication (SSL/TLS) . If the time difference between devices is too large (typically more than a few seconds), the Control Plane cannot validate the certificates, leading to a failure in the trust relationship .

ConfigSync Failure : When device trust is broken due to time drift, the systems cannot verify the identity of the peer, which directly prevents the ConfigSync process from executing on the affected device, such as bigip3.local in this scenario.

Resolution : Administrators must ensure that all devices in a high availability pair are configured to use the same reliable NTP servers to keep their system clocks aligned.

The correct command for restoring an encrypted UCS archive via the command line is D. load /sys ucs < filepath > passphrase < password > .

On a BIG-IP system, remote syslog server configuration is managed through the logging configuration framework. In the Configuration Utility, this is accessed via:

System > Logs > Configuration

This section allows the administrator to:

Define remote syslog destinations

Configure log publishers

Control which log types (system, audit, LTM, ASM, etc.) are forwarded to external syslog servers

Why the other options are incorrect:

A. System > Configuration > Local Traffic Used for traffic management settings, not logging.

C. System > Logs > Audit Displays audit log settings and content but does not configure remote syslog destinations.

D. System > Configuration > Device Used for device-level settings such as hostname and platform configuration, not logging.

Therefore, the correct location to reconfigure BIG-IP to send logs to new syslog servers is System > Logs > Configuration .

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Management access security is a primary Control Plane configuration task3.

Management Interface Security: The BIG-IP system provides a dedicated management port that is separate from the TMM (Traffic Management Microkernel) data interfaces 4444 .

System Platform Settings: Under the System > Platform section of the Configuration Utility, an administrator can define specific IP addresses or subnets that are permitted to access the device via SSH or HTTPS (the GUI).

Port Lockdown Difference: While " Port Lockdown " settings under Network > Self IPs control access to the device through self-IP addresses on data VLANs, they do not manage the security of the dedicated management port .

Access Control Lists: For robust security, F5 recommends using the " IP Allow " or " httpd Allow " lists found in the platform settings to prevent malicious brute-force attempts or unauthorized access from non-management networks .

When troubleshooting a BIG-IP system where a partition is reported as full (100% utilization), identifying and removing large or unnecessary files is the immediate next step for restoration of system stability.

Symptoms of Full Partitions : If a file system (such as the root / or /var) becomes full, it can result in unpredictable system behavior, failure to save configurations, and the inability to log in to the Web UI.

The Root (/) Partition : This partition is intentionally kept small on F5 systems. It is highly sensitive to the storage of third-party software or diagnostic files that should ideally be stored in the /shared or /var directories.

Procedural Resolution : To resolve 100% disk usage, administrators should check for large files on the affected partition using CLI commands like du -ah or find / -xdev -type f -exec du {} \; | sort -rn | head -20.

Common Culprits : Large files typically causing these issues include old core files, tech support bundles, large diagnostic logs (packet diags), or temporary files created during administrative tasks.

Diagnostics vs. Remediation : While tests like the EUD (End User Diagnostics) or platform diagnostics are useful for hardware verification, they do not resolve file system exhaustion issues that have already reached a critical 100% state.