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Uneven load balancing on a BIG-IP system typically occurs when traffic is not distributed evenly across all available pool members. One common reason is thatmonitors have marked down multiple pool members (Option B). When health monitors fail for specific pool members, BIG-IP automatically removes those members from load-balancing decisions. As a result, traffic is sent only to the remaining healthy member, creating the appearance that load balancing is not functioning correctly. This behavior is expected and aligns with BIG-IP’s design to ensure traffic is sent only to healthy resources.

Another frequent cause isthe presence of a persistence profile on the pool or virtual server (Option C). Persistence (such as source address or cookie persistence) forces subsequent client connections to be sent to the same pool member for session continuity. While persistence is critical for certain applications, it can override the load-balancing algorithm and cause most or all traffic to be directed to a single pool member, especially during low traffic volumes or testing scenarios.

The other options are incorrect because avirtual server marked down (Option A)would not pass traffic at all, andall pool members marked down (Option D)would result in no connections rather than uneven distribution. This analysis follows standard BIG-IP troubleshooting methodology using pool status, monitor results, and persistence configuration review.

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

These log messages indicate that the BIG-IP system’sTraffic Management Microkernel (TMM)has enteredaggressive eviction modedue tohigh global memory utilization. When TMM memory consumption reaches critical thresholds, BIG-IP activates thedefault eviction policyto protect system stability and prevent a full traffic processing failure. This condition directly corresponds toOption A, where the global eviction policy is triggered because TMM memory resources are nearing exhaustion.

Once aggressive mode is activated, BIG-IP begins using theconnection sweeper mechanism, which selectively terminates existing connections to free memory. The repeated log entries stating“1 connections killed”confirm that the system isreaping some connections, not all connections. This behavior matchesOption C. The eviction process is incremental and controlled, targeting idle, low-priority, or least-recently-used connections first to minimize impact on active traffic.

Option B is incorrect because BIG-IP doesnotdrop all connections during aggressive mode; it only removes enough connections to relieve memory pressure. Option D is also incorrect because TMM eviction is based onTMM global memory usage, not swap memory utilization. TMM does not rely on swap space in the same way the host Linux system does.

These messages are a critical warning sign that the system is under memory stress and may require traffic optimization, connection limits, or hardware scaling.

According toofficial F5 documentation (K52015891 – Troubleshooting BIG-IP power supply issues),hardware-related alerts for power supplies, fans, and chassis components are logged in /var/log/ltm.

When a BIG-IP device experiences a power supply issue—such as failure, intermittent outages, or fan-related faults—the system generates alerts through internal platform monitoring services. These alerts are written to the/var/log/ltmfile and often appear with messages similar to:

Chassis power supply 2 has experienced an issue. Status is as follows: FAN=bad; STATUS=bad.

This makes /var/log/ltm theauthoritative log filefor identifying and verifying power supply and chassis-related problems on BIG-IP systems.

The other log files are not appropriate for this purpose:

/var/log/daemon.logcontains general daemon messages but isnot the primary sourcefor chassis hardware alerts.

/var/log/kern.loglogs kernel-level events, not platform power status.

/var/log/auditrecords administrative actions and configuration changes.

Conclusion:

Per F5-supported guidance, when suspecting power supply outages or chassis hardware issues, the BIG-IP Administrator shouldalways check /var/log/ltm first.

Before upgrading a BIG-IP system to a newer TMOS version, it is critical to review known issues to avoid introducing instability or regressions.F5 Bug Tracker (Option B)is a primary resource for this purpose. It allows administrators to search for documented software defects by TMOS version, module, symptom, or bug ID. Using Bug Tracker, an administrator can identify unresolvedissues, fixed bugs, and behavioral changes that may affect their specific deployment, such as traffic handling, high availability, or module-specific functionality. This directly supports proactive troubleshooting and informed upgrade planning.

F5 iHealth (Option D)is another essential tool used during upgrade preparation. iHealth analyzes uploaded UCS or QKView files and correlates the device configuration and software version with F5’s known issues database. It provides actionable reports highlighting critical defects, upgrade risks, interoperability concerns, and recommended target versions. iHealth is especially valuable because it contextualizes known issues based on the actual configuration running on the device.

The other options are not appropriate for verifying known software issues.F5 End User Diagnostics (Option A)is a client-side troubleshooting tool,F5 University (Option C)is a training platform, andF5 Downloads (Option E)is primarily used to obtain software images and release notes, not to analyze known defects in depth.

Comprehensive and Detailed Explanation From BIG-IP A41dministration Support and Troubleshooting documents:To confirm functionality across a complex environment, the "Network Map" is the most efficient troubleshooting tool in the Configuration Utility43. It provides a hierarchical, visual representation of the traffic management objects44. A single glance allows the administrator to see the status of a Virtual Server (Green/Red/Yellow), the status of its associated pool, the health of individual pool members, and which iRules are currently attached45. This view is superior to the standard "Virtual Server List" for troubleshooting because it maps the dependencies between objects46. For example, if a Virtual Server is "Red," the Network Map will show if that status is inherited from a failed pool or a specific monitor failing on a pool member. Reviewing these basic stats in the Network Map helps the administrator quickly isolate whether a failure is at the service level (Virtual Server), the logic level (iRule), or the hardware level (Pool Member).

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.

When a virtual server's traffic flow is disrupted only during failover events and takes several minutes to stabilize, the issue is typically related to the ARP cache on upstream network devices47. By default, each BIG-IP in an HA pair uses its own unique hardware MAC address for traffic4848. When a failover occurs, the new active device takes over the floating IP addresses, but the upstream switch may still have the MAC address of the old device cached4949. Traffic fails until the switch's ARP entry is updated. "MAC Masquerade" is a troubleshooting feature that assigns a shared, virtual MAC address to the floating traffic group. Regardless of which BIG-IP is currently active, it will use this masqueraded MAC address for all traffic related to that group52. Because the MAC address seen by the network never changes during a failover, the upstream devices do not need to relearn ARP entries, resulting in an instantaneous transition and eliminating the performance drop reported by users

Comprehensive and Detailed Explanation From BIG-IP Administration S73upport and Troubleshooting documents: Persistence is critical for ensuring that a client's session remains with the same pool member throughout its duration. If primary persistence (like Cookie Persistence) fails—for instance, because the client has disabled cookies—load balancing will not work as expected, and the session may be broken. A "Fallback Persistence Profile" provides a backup method75. The most common and reliable fallback method is "Source Address Affinity"76. This method tracks the client's IP address in the BIG-IP's persistence table and ensures that any subsequent requests from that IP are routed to the same pool member, even if the primary persistence token is missing. Troubleshooting session drops often involves checking if a fallback method is configured to handle scenarios where the primary method is unsupported by the client's browser or environment. Without a fallback, the BIG-IP would revert to standard load balancing, potentially sending the client to a different server that lacks their session data.

Monitoring granular resource utilization is essential when troubleshooting performance degradation for specific applications. While global system stats show overall hardware health, they do not pinpoint which virtual server is overconsuming resources during traffic spikes. To identify the specific application causing a high CPU load, the administrator should navigate to Statistics > Module Statistics > Local Traffic > Virtual Servers7474. This section provides detailed metrics for each virtual server, including CPU cycles used for traffic processing and iRule execution75. Identifying a "top-talker" or a problematic virtual server allows the administrator to take targeted action, such as optimizing an inefficient iRule, adjusting compression levels, or offloading the virtual server to a different device group76. This targeted troubleshooting ensures that one high-demand virtual server does not negatively impact the performance of other services running on the same BIG-IP hardware, maintaining overall system stability and resource availability

AQKViewis the primary diagnostic file used by F5 Support to analyze BIG-IP system health, configuration, performance, and logs. It collects a wide range of data, including running configuration, license details, module provisioning, hardware status, logs, statistics, and diagnostic command output. Generating a QKView is a standard first step when troubleshooting issues or opening a support case with F5.

In the BIG-IP Configuration Utility (GUI), the correct location to generate a QKView isSystem > Support (Option C). This menu is specifically designed for support and troubleshooting activities. From this section, administrators can create QKView files, upload them directly to F5 iHealth, or download them locally for later analysis or submission to F5 Support.

The other options are incorrect:

System > Configuration (Option A)is used for system-wide settings such as device name, NTP, and DNS.

System > Archive (Option B)is used to create UCS backups, not diagnostic QKViews.

System > Logs (Option D)is used to view and manage log files, not to generate support bundles.

This workflow is clearly documented in BIG-IP Administration and Support guides and is considered a best practice for efficient troubleshooting and support engagement.