F5CAB4 BIG-IP Administration Control Plane Administration (F5CAB4) exam Questions and Answers

A QKView is a comprehensive snapshot of the device's Control Plane state, configuration, and logs used for troubleshooting. By default, the qkview utility stores its generated output file in the /var/tmp/ directory. Administrators must know this path to retrieve the file for upload to F5 iHealth or Support.

This log message indicates that the system is low on memory and has activated 'Aggressive Mode' to reclaim resources by closing old connections37. In an HA environment, one way to ensure state stability during memory pressure is to manage how connection data is handled38. While the document suggests D, procedural mitigation for 'Aggressive Mode' often involves reviewing resource provisioning or optimizing connection idle timeouts to reduce memory footprint39.

A BIG-IP device group cannot be deleted if it still contains device members, even if one of those devices has already been decommissioned or is unreachable. Before deleting the device group, the administrator must explicitly remove the decommissioned device from the device group configuration.

Once the removed or unreachable device is deleted from the device group membership, the BIG-IP system allows the remaining administrator to successfully delete the device group.

Why the other options are incorrect:

A. Remove all members from the device groupThis is not required; the key requirement is removing the decommissioned device, not all members.

B. Make sure all members are in syncSynchronization status does not prevent device group deletion.

D. Disable the device groupDevice groups cannot be disabled; they must be modified or deleted.

Therefore, the correct prerequisite action is to remove the decommissioned device from the device group, making C the correct answer.

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

tmsh create auth user 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.

Comprehensive and Detailed Explanation From BIG-IP Administration Control Plane Adminis44tration documents: In a45n Active/Standby HA pair, application traffic only flows through the Active device. If an administrator makes a change on the Standby device (which has no traffic), they must synchronize the configuration to the Active device to test it. The procedural step is to log into the Active device and "pull" the configuration from the Standby device (or push from Standby) so the Active device can process traffic using the new iRule

Time synchronization is a critical component of Control Plane management, as it ensures that logs are accurately timestamped and that High Availability (HA) trust relationships remain valid1.

Configuration Location: The list of configured NTP (Network Time Protocol) servers and their status is managed under System > Configuration > Device > NTP .

Procedural Importance: If the system clock drifts significantly between two devices in an HA pair, the Control Plane may experience a "Time Delta" error33. This drift often causes a failure in device trust, preventing the ConfigSync process from functioning correctly.

System Integrity: Accurate time is also essential for the validity of SSL/TLS certificates used for both administrative management access and high availability communication.

Verification: Administrators can use this section of the Configuration Utility to confirm that the BIG-IP is communicating with its designated upstream time sources and that the local clock is correctly synchronized to the network environment .

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>.

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.

Management connectivity is protected by an allowed access list for the httpd daemon. Unlike TMM data ports which use 'Port Lockdown' settings, the management port's access is controlled by a specific 'Allow' list. If an administrator's IP is not explicitly included in this list, the Control Plane will reject HTTPS connection attempts to the management utility.

Managing the state of a device often involves restoring configuration backups known as User Configuration Set (UCS) files These archives contain the full system configuration, including licenses and SSL certificates. The Control Plane provides a dedicated management area for these files under System > Archives, where administrators can upload, create, and restore configuration snapshots

The BIG-IP Control Plane monitors the "Commit ID" of the configuration on all group members. When a change is made on the Standby unit, it becomes the member with the most recent configuration. The "Recommended Action" in the HA status dashboard will be to synchronize that specific device's configuration to the rest of the group to ensure consistency

When a failover occurs, the newly active device must inform the surrounding network that it now "owns" the shared IP addresses. Without MAC Masquerade, the new device uses its own hardware MAC, requiring upstream routers to update their ARP tables (which causes a delay). MAC Masquerading allows the HA pair to share a "floating" MAC address, ensuring the Control Plane transition is transparent to the network layer

The User Configuration Set (UCS) is a flexible tool designed by the Control Plane to handle various lifecycle management scenarios, including upgrades and hardware migrations.

Version Compatibility (Option B): TMOS is designed to be backward compatible. The Control Plane can ingest a UCS file created on an older version of software and automatically upgrade the configuration objects to match the current, later version during the restore process.

Platform Portability (Option C): While a UCS archive contains platform-specific information, the BIG-IP system allows for "platform-independent" restores. This is a vital procedural concept for migrating from one hardware model to another or from physical hardware to a Virtual Edition (VE).

Management of State: When restoring to a different platform or a later version, the administrator often uses specific flags (such as no-license or platform-migrate in later versions) to ensure that only the portable configuration data is applied while preserving the new platform's unique identifiers.

Management of the device's identity and primary out-of-band connectivity is a central Control Plane responsibility.

Platform Settings: The System > Platform section of the Configuration Utility is used to manage global hardware and system parameters, including the hostname, management IP address, and time zone.

Management vs. Data Plane: It is critical to distinguish between the management interface and TMM data interfaces. While data plane IPs (Self IPs) are configured under Network > Self IPs, the dedicated management port settings are grouped with other platform-level configurations.

Access Control: This area is also used to manage administrative security, such as restricting SSH or HTTPS access to specific management subnets or IP addresses.

Impact of Change: Changing the management IP will immediately disconnect any active GUI or SSH sessions using the current management IP. The administrator must reconnect using the newly assigned address.

watch-devicegroup-device shows (among other columns) the commit ID (cid.id / shown here as clu_id), the originating device for that commit (cid-orig / shown here as cl_orig), and the time the configuration change was made (cid.time / shown here as cl_time). The highest/newest commit ID and its time represent the most recent configuration change seen among the devices. (clouddocs.f5.com)

bigip_a has the latest configuration (A) because it shows commit ID 3273 at 14:27:00, which is newer than commit ID 1745 at 13:52:34 on bigip_b and bigip_c. (clouddocs.f5.com)

Two devices are out of date (B) because bigip_b and bigip_c are still on the older commit ID 1745, so they do not match the latest commit shown on bigip_a. (clouddocs.f5.com)

Why the other options are not supported by this output:

C is not supported: bigip_c is not showing a newer commit than the others; it’s on the older commit (1745), so it’s not the source of the most recent change. The output’s cid-orig column is what tells you where the change was made. (clouddocs.f5.com)

D/E are incorrect logic: matching cid.time between two devices only indicates they share the same change timestamp/commit, not that it is the correct or latest configuration. The “latest” is indicated by the newest commit ID/time (here, bigip_a). (clouddocs.f5.com)

Comprehensive and Detailed Explanation From BIG-IP Administration20 Control Plane Administration documents: Connectivity management involves ensuring that the physical layer matches the networking environment. Interface properties, including media speed, duplex settings, and MTU, are managed at the Control Plane level under the Network menu. To resolve a mismatch with an upstream switch, the administrator must navigate to Network > Interfaces to manually override auto-negotiation settings.

On BIG-IP systems, authentication and authorization events are logged in /var/log/secure. This includes:

Successful and failed SSH login attempts

Invalid user authentication attempts

PAM (Pluggable Authentication Module) authentication failures

Access denials related to secure services

Why the other options are incorrect:

/var/log/messages contains general system messages and service events, not detailed authentication failures.

/var/log/audit records administrative configuration changes (who changed what and when), not login attempts.

/var/log/ltm logs traffic-management (TMM) and application-related events.

Therefore, the correct log file for investigating unauthorized SSH login attempts is /var/log/secure.

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