F5 F5CAB5 Dumps

The key clue in the exhibit is the pool member’s availability showing“Offline (Enabled) – Parent down”. In BIG-IP terminology, a pool member inherits the status of itsparent node. If thenodeis marked down (for example, by a node-level monitor or a default “node is down” condition), thenall pool members using that node IPwill also be marked down and will not receive any traffic, even if the application service on the member port might be healthy.

While the HTTPS monitor configuration (send/receive strings) is displayed, the statusspecificallyindicates anode (parent) failure, not a service-level failure. If the problem were the application not matching the receive string, you would typically see the member down due to themember’s monitorfailing (and the status would reflect monitor failure details), rather than “parent down.”

Option D is too broad; BIG-IP can generally reach the subnet (other servers work), and this symptom points to a specific node condition. Option C is incorrect because HTTP/1.1 is commonly used for monitoring and is valid when properly formatted (especially with a Host header). Therefore, the most likely cause is that thenode health monitor is not responding, causing the node—and consequently the member—to be marked down.

Comprehensive and Detailed 150 to 250 Words Explanation From BIG-IP Administration, Support, and Troubleshooting Documents:

AQKViewfile is the primary diagnostic support bundle used by F5 Support to troubleshoot BIG-IP system issues. It contains comprehensive system information, including running configuration, licensing details, module provisioning, hardware status, software versions, log files, statistics, and the output of numerous diagnostic commands. Generating a QKView is a standard and recommended first step when investigating performance problems, configuration issues, or when opening a support case with F5.

In the BIG-IP Configuration Utility (GUI), the correct and supported location to generate a QKView isSystem > Support. This menu is specifically designed for support and troubleshooting operations. From this section, administrators can generate a QKView file, monitor its creation progress, download it locally, or upload it directly to F5 iHealth for automated analysis. This workflow is clearly documented in BIG-IP Administration and Support guides and aligns with F5 best practices.

The other menu options are not appropriate:

System > Configurationis used for system-wide settings such as DNS, NTP, and device identity.

System > Archiveis used to create UCS backup files, which are configuration backups, not diagnostic bundles.

System > Logsis used only for viewing system logs, not generating support files.

Therefore,System > Supportis the correct and only valid answer.

The End User Diagnostics (EUD) utility is a hardware-level testing suite used to verify the integrity of the physical components of a BIG-IP appliance.

Access Requirements: Because the EUD must be run while the TMOS operating system is not loaded (typically when the device cannot boot or requires hardware validation), it cannot be accessed via network-based interfaces like the Management Port or VLANs.

Console Connection: The administrator must connect a terminal to the physical Console Port (using a serial cable) to interact with the boot menu.

Execution Process: Upon restarting the appliance, the administrator must intercept the boot process at the GRUB menu and select the "End User Diagnostics" option. All output and menu selections are then handled through the serial console session.

When load balancing is not working as expected across hardware hosting multiple services, the administrator must distinguish between "member" and "node" level algorithms102102102102. A "member" is a specific IP and port (e.g., 10.1.1.1:80), while a "node" is the physical server's IP (10.1.1.1) regardless of the port103. If servers host both FTP and HTTP services in separate pools, using "Least Connections (Member)" only balances connections within each individual pool. This can lead to a skewed distribution where one server is selected for a new HTTP connection because it has the fewest HTTP connections, even if it is currently overloaded with hundreds of FTP connections. By applying "Least Connections (Node)," the BIG-IP tracks the total number of connections to the physical hardware across all ports and pools106106106106. This ensures that the administrator can maintain an even distribution of the total workload across the server fleet, resolving the reports of uneven traffic distribution reported by the server support team

In complex network environments, "SNAT Automap" is frequently used to ensure that backend servers send return traffic through the BIG-IP. However, SNAT hides the original client's IP address, replacing it with the BIG-IP's self-IP. When interpreting traffic flow for security or logging purposes, backend servers often need that original IP. To resolve this without breaking the network-layer routing provided by SNAT, the administrator should apply an HTTP profile to the virtual server and enable the "Insert X-Forwarded-For" option. When this is enabled, the BIG-IP inserts a standard HTTP header containing the client's original IP address before forwarding the request to the pool member. This troubleshooting method allows the backend application to log the actual user's identity while maintaining a functional L3/L4 traffic flow where the server responds to the BIG-IP's local address. This is a standard troubleshooting solution for "web server not working as expected" scenarios where applica8tion logic depends on knowing the geography or specific identity of the connecting user.

To utilize the F5 iHealth service, a BIG-IP Administrator must generate a diagnostic snapshot of the system known as a QKView file.

GUI Path: In the BIG-IP Configuration Utility (GUI), the QKView generation tool is located under System > Support.

Process: On the Support page, the user selects the "New Support Snapshot" button. From there, they ensure "QKView" is selected. Once the BIG-IP finishes collecting the data (which includes logs, configuration, and hardware statistics), the user can download the resulting .qkview file directly to their local machine.

iHealth Integration: This file is then uploaded to ihealth.f5.com. The Upgrade Advisor tool within iHealth specifically parses this QKView to check the current configuration against known bugs, hardware limitations, or syntax changes in the target TMOS version.

Evaluation of Other Options:

System > Configuration (Option B): This section contains general system settings like DNS, NTP, and SNMP, but does not contain diagnostic tools.

System > Software Management (Option C): This is where new TMOS images (.iso files) are uploaded and installed, but it is not used for generating diagnostic reports.

System > Archives (Option D): This is used to create and manage UCS (User Configuration Set) files, which are full system backups. While UCS files contain configuration, they do not contain the deep diagnostic logs and hardware stats required by iHealth for an Upgrade Advisor analysis.

The "Manual Resume" feature is a safety mechanism used when a pool is not working as expected due to flapping services or unstable backend applications. Normally, when a health monitor fails, the pool member is marked "Offline" (Red), and when the monitor passes, it automatically returns to "Available" (Green)47. However, if "Manual Resume" is enabled, the BIG-IP will not automatically put the member back into rotation after a failure48. Even if the health check begins to pass again, the member remains in an "Offline (Disabled)" state49. This requires an administrator to manually intervene and re-enable the member. This is a common point of confusion when troubleshooting; a member may show passing health checks but still not receive traffic because it is waiting for a manual administrative "resume" command. This feature is intended to prevent "unhealthy" servers from receiving traffic until an engineer has confirmed the root cause of the initial failure was resolved.

To ensure a support case is processed and routed efficiently, F5 specifies a mandatory set of baseline information.

Serial Number: Required to verify the support contract and entitlement level for the hardware or virtual edition.

QKView: This is described as the "first and most important thing to have when opening a case". It provides the F5 Support Engineer with the necessary diagnostic data to understand the system's current state and resource utilization.

Problem Description: A precise description of the issue, including symptoms, when the problem started, and the business impact, is critical for routing the case to the correct technical team.

Contact Info: Accurate contact information for the individual who will be working on the ticket with F5.

Comparison: While packet captures (Option A) or UCS files (Option B) are often useful, they are not strictly required for the initial opening of all support tickets; however, a QKView is considered a primary prerequisite for technical analysis.

On a BIG-IP system, hardware-related alerts, including those for power supply units (PSUs), fans, and chassis components, are primarily logged in the Local Traffic Manager (LTM) log file.

Log Location: The file path is /var/log/ltm.

PSU Alert Messages: When a power supply fails, experiences an outage, or is unplugged, the chmand (Chassis Manager) or system_check processes log specific error codes to this file. For example, you may see messages like 010d0006:0: Chassis power supply has experienced an issue or VINPUT=bad.

Troubleshooting: Administrators can use the command grep -i "power supply" /var/log/ltm to quickly filter for PSU-related events.

Other Logs: * /var/log/kern.log typically contains low-level kernel and driver messages.

/var/log/audit tracks administrative changes and commands executed by users.

/var/log/daemon.log contains messages from various system background services but is not the primary location for hardware sensor alerts.

The BIG-IP architecture is divided into two distinct planes: the Control Plane (Management) and the Data Plane (Traffic Management Microkernel - TMM).

Data Plane (TMM): This plane is responsible for the actual processing of application traffic, including load balancing, SSL offloading, and session management for modules like APM (Access Policy Manager). If data plane resources (CPU/Memory allocated to TMM) are exhausted, active user sessions and traffic throughput are directly degraded.

APM Sessions: Because APM sessions are managed within the TMM process to ensure high-speed access control and tunneling, they are a primary "Data Plane" function.

Control Plane Functions: Options A, B, and D (MCPD, Configuration Utility/GUI, and iControl) all reside in the Control Plane (running on the Linux host OS). While a total system hang affects both, a specific "data plane resource issue" is designed to isolate and impact the traffic-handling services like APM while the management GUI might remain responsive.

Monitoring resource utilization is essential for maintaining system stability. If the root (/) file system reaches 100% capacity, the BIG-IP may become unresponsive, fail to save configuration changes, or experience daemon crashes83. When the / partition is full, the immediate troubleshooting step is to identify large or unnecessary files—such as old log files, core dumps, or temporary installer files—located specifically within that file system84. In the provided exhibit, /dev/md4 is explicitly listed at 100% usage for the / mount point85. Checking other partitions like /usr (which is at 82% in the exhibit) would not resolve the immediate "Full" status of the root directory86. Administrators often use the du (disk usage) command via the CLI to find the problematic files. Managing disk space is a proactive task; however, when utilization hits 100%, it becomes a reactive troubleshooting emergency that must be resolved to restore the management plane's functionality.

A gateway_icmp monitor checks basic network reachability by sending ICMP echo requests (pings) to the pool member or its gateway. If the pool is markedDOWNwhile the server is confirmed to be online, the most likely cause is thatICMP traffic is being blocked.

Ahost-based firewall active on the server (Option C)can block ICMP echo requests or replies, preventing BIG-IP from receiving a successful response to the health check. This results in the monitor failing and the pool member being marked down, even though the server and application are otherwise functioning normally. This explanation is consistent with the scenario where other servers in the same subnet work correctly, indicating that routing and BIG-IP configuration are not the issue.

The other options are unrelated to ICMP monitoring. Logged-in users (Option A), missing patches (Option B), and stopped HTTP services (Option D) do not affect a gateway_icmp monitor. BIG-IP troubleshooting best practices recommend verifying ICMP reachability and firewall policies when diagnosing ICMP-based monitor failures.

F5 recommends using the iHealth diagnostic tool to identify security vulnerabilities and receive specific remediation guidance.

QKView and iHealth: A QKView file is a comprehensive diagnostic snapshot of the BIG-IP system. When this file is uploaded to the F5 iHealth portal, it is automatically parsed against a database of known issues and security advisories.

Vulnerability Diagnosis: The iHealth platform includes automated checks specifically designed to surface security gaps and "Heuristics" that match the system's current configuration and software version to known CVEs (Common Vulnerabilities and Exposures).

Remediation Guidance: For every identified vulnerability, iHealth provides direct links to the relevant F5 Security Advisory (K-article), which contains detailed remediation steps, such as specific software versions that contain a fix or temporary mitigation commands.

UCS vs. QKView: While a UCS (User Configuration Set) file is a backup of the system configuration, it is not the format used by the iHealth diagnostic engine for automated vulnerability scanning; the QKView is the required format for this process.

The Local Traffic Manager (LTM) log file is the primary repository for all events related to load balancing objects, including virtual servers, pools, and nodes.

Monitor Logging: When a health monitor marks a pool member as "UP" or "DOWN," the system generates a log entry in /var/log/ltm.

Diagnosing Flaps: To troubleshoot "flapping" (frequent state changes), an administrator would look for messages like 01010028:3: Pool /Common/http_pool member /Common/10.10.1.1:80 monitor status down followed quickly by an "up" status. This log provides the timestamp and the specific monitor that triggered the state change.

This virtual server is intended to function as aforwarding (IP-forwarding) virtual server, which is commonly used for routing or firewall-style deployments where BIG-IP forwards traffic transparently without load balancing or address translation. For a forwarding virtual server to match and passall traffic, the destination must be configured as 0.0.0.0:anywith a mask of 0.0.0.0, not 255.255.255.255.

The configured mask 255.255.255.255 represents a/32 host mask, which restricts the virtual server to matching traffic destined only for the exact IP address 0.0.0.0. Since 0.0.0.0 is not a valid routable destination for normal traffic, no packets will ever match the virtual server, causing it to pass no traffic at all.

This is a well-documented BIG-IP behavior:

destination 0.0.0.0:any

mask 0.0.0.0

together define acatch-all forwarding virtual server.

The destination itself (Option A) is correct for a forwarding VS, and disabling address translation (Option C) is expected and required for IP-forwarding mode. Therefore, the incorrect subnet mask is the sole reason the virtual server is not functioning as expected.

In BIG-IP TMOS administration, the "Forwarding (IP)" virtual server type is unique because it is designed to act as a high-performance router rather than a typical load balancer. Unlike a "Standard" virtual server, which terminates a connection and directs it to a specific pool of members, a Forwarding (IP) virtual server is intended to forward packets based on the system’s routing table. Consequently, the configuration for this type of virtual server explicitly removes the option to associate a default pool. If an administrator is troubleshooting a scenario where they cannot assign a pool to a virtual server, they must verify if the type was accidentally set to Forwarding (IP). This type is most commonly used for outbound internet traffic (outbound SNAT) or to allow the BIG-IP to serve as a gateway between internal subnets. Identifying this constraint is vital for troubleshooting configuration errors where an administrator expects the system to load balance traffic but finds the pool association settings are grayed out or unavailable in the Configuration Utility.

The primary reason for the uneven traffic distribution is the presence of a Persistence Profile in the virtual server configuration.

Load Balancing vs. Persistence: While the Round Robin method is designed to distribute new connections sequentially among pool members, Persistence overrides this logic for existing clients.

Source Address Persistence: The configuration shows source_addr persistence is enabled. This ensures that once a client (identified by their source IP) is mapped to a pool member, all subsequent connections from that same IP will be sent to the same member for the duration of the persistence record.

Uneven Distribution Logic: If one source IP address generates significantly more connections or longer-lived sessions than others—or if many clients appear behind a single NAT/Proxy IP—that specific pool member (in this case, 172.16.20.3) will receive a disproportionate amount of traffic compared to the others.

Evaluating Other Options:

Automap (Option A): SNAT Automap changes the source IP between the BIG-IP and the pool member. It does not impact the BIG-IP's ability to load balance incoming client requests.

Ratio Settings (Option B): In the provided exhibit, the pool members have a Ratio of 1, 2, and 3 respectively. While a higher ratio does direct more traffic to a member, the question asks for the "most likely cause" in the context of the provided ltm virtual configuration, which explicitly highlights the persistence override.

HTTP Profile (Option C): Round Robin is a Layer 4 load balancing algorithm and does not require a Layer 7 HTTP profile to function.

These log messages indicate that the BIG-IP system is under significant resource pressure and has activated its Adaptive Connection Management.

Global Eviction Policy: The message Aggressive mode ... activated (global memory) confirms that the system has reached a memory utilization threshold that triggers the eviction policy. This happens because TMM (the data plane) is running low on available memory pages.

Sweeper/Reaping: Once in "Aggressive mode," the BIG-IP "sweeper" starts reaping (terminating) connections to free up memory. The log Connections killed confirms this is occurring.

Impact: The system does not drop all connections; it targets connections based on the eviction policy (e.g., oldest connections or those exceeding limits) to bring memory usage back to safe levels. Thus, some connections will be dropped (Option A), and the cause is TMM memory exhaustion (Option C).

Status changes for local traffic objects (Virtual Servers, Pools, Nodes) are recorded in the Local Traffic Manager (LTM) log.

Health State Logging: When a health monitor marks a resource as available (Green) or unavailable (Red), the system generates a log message in /var/log/ltm.

Log Entry Example: A transition from Red to Green will appear as a message similar to: 01010027:3: Pool /Common/my_pool member /Common/10.0.0.1:80 monitor status up.

Evaluation of Other Options:

/var/log/audit (Option A) logs who changed a configuration, not automated state changes from health monitors.

/var/log/lastlog (Option C) is a standard Linux file that tracks the last login time of users.

/var/log/monitors (Option D) is not a standard log file on the BIG-IP system.