F5 BIG-IP Administration Support and Troubleshooting (F5CAB5) exam F5CAB5 Exam Dumps: Updated Questions & Answers (February 2026)

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

In the BIG-IP Configuration Utility, the status icon (shape and color) provides immediate feedback on why a virtual server is not working as expected81. A "Red Diamond" indicates that the object is "Offline" and unavailable to process traffic82. For a virtual server, this specific status typically means it has inherited an offline state from its mandatory backend resources8383. If all pool members associated with the virtual server have failed their health monitors, the virtual server will transition to a red diamond status because it has no healthy destination for incoming requests. This is distinct from a "Black Circle," which would indicate the virtual server has been manually "Disabled" by an administrator85858585. To troubleshoot a red diamond, the administrator must examine the associated pool and its members to determine why the health monitors are failing (e.g., server crashes, network path failures, or incorrect monitor strings). Resolving the health check failures on the pool members will return the virtual server to an "Available" (Green) status.

The BIG-IP system uses the audit log to track administrative actions and configuration changes.

Audit Logging Functionality: When a user modifies the configuration via the Configuration Utility (GUI), the Traffic Management Shell (tmsh), or iControl, the system records the event in the audit log. This includes the name of the user who made the change, the timestamp, and the specific command or object that was modified.

Log Location: The audit log is stored at /var/log/audit.

Evaluation of Other Options:

/var/log/messages (Option A) contains general system and kernel messages but is not the primary source for configuration change details.

/var/log/secure (Option B) primarily logs authentication and authorization attempts (logins and logouts).

/var/log/user.log (Option D) is a generic Linux log file for user-level applications and does not track BIG-IP LTM configuration changes.

When adding new members to an active, high-traffic pool, the Slow Ramp Time setting is critical for maintaining application stability.

Mechanism: The Slow Ramp Time feature (located in the Pool properties) allows the BIG-IP system to gradually increase the number of connection requests sent to a newly added or recently enabled pool member.

The Issue: In a highly utilized pool, if Slow Ramp Time is set to 0 (the default), the BIG-IP immediately begins sending a proportional share of traffic to the new members. If the application requires a "warm-up" period (e.g., to build local caches or establish database connection pools), the sudden influx of traffic can overwhelm the new server, causing it to drop requests or fail to load content for users.

Recommendation: F5 recommends setting a non-zero Slow Ramp Time (measured in seconds) to allow the new member to scale up its processing capacity incrementally.

This scenario describes a classic network performance issue known as the "Mega-Proxy" problem. When an organization routes all employee traffic through a single proxy server, the BIG-IP sees thousands of unique users as having the exact same source IP address. If the administrator has configured "Source Address Affinity" persistence, the BIG-IP will correctly follow the rule but incorrectly route all users to the same single backend pool member. This creates a severe load imbalance where one server is overwhelmed while others remain idle, leading to poor application response times. To resolve this, the administrator must change the persistence profile to "HTTP Cookie". Cookie-based persistence allows the BIG-IP to place a unique identifier in each user's browser, allowing the system to distinguish between individual sessions even if they share the same source IP. This fix ensures that traffic is distributed evenly across the pool members, restoring4 the expect5ed load balancing functionality and resolving the slow performance reported by users behind the corporate proxy.

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.

To successfully performSSL offload and re-encryptionon a BIG-IP system, the virtual server must be configured withboth a Client SSL profile and a Server SSL profile. The Client SSL profile enables BIG-IP to decrypt inbound HTTPS traffic from clients, while the Server SSL profile is required tore-encrypt traffic before forwarding it to the pool members.

From the exhibit, the virtual server has aClient SSL profile configured, which allows BIG-IP to accept HTTPS connections from clients. However, there isno Server SSL profile attached, meaning BIG-IP attempts to sendunencrypted HTTP trafficto pool members listening on HTTPS (port 443). This protocol mismatch causes the server-side SSL handshake to fail, resulting in users being unable to connect to the application.

This behavior is well documented in BIG-IP SSL troubleshooting guides: when backend servers expect HTTPS, a Server SSL profile is mandatory to establish a secure connection from BIG-IP to the pool members.

The other options are incorrect:

Removing the Client SSL profile (Option A) would break client-side HTTPS.

The server-side TCP profile (Option B) is unrelated to SSL encryption.

Forward Proxy (Option C) is only used for outbound SSL inspection scenarios.

Therefore, configuring anSSL Profile (Server)is the correct and required solution.

When load balancing is not working as 23expected and connections appear skewed across physical hardware, the administrator must distinguish between "member"24 and "node" level balancing. A "member" refers to a specific IP and Port combination (e.g., 10.1.1.1:80), whereas a "node" refers to the underlying IP address (10.1.1.1) regardless of the port25. If a single server hosts multiple services (Web, FTP, API) across different pools, using "Least Connections (member)" would only balance connections within each individual pool26. This could lead to a scenario where one server is overwhelmed because it is winning the "least connections" count in three different pools simultaneously. By selecting "Least Connections (node)," the BIG-IP tracks the total number of concurrent connections to the physical IP address across all pools it belongs to27. This ensures that the administrator can maintain an equal distribution of work across the hardware, preventing performance degradation on backend servers that host multiple application services.

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.

F5 BIG-IP provides two distinct ways to throttle traffic on a Virtual Server: total capacity and velocity.

Connection Rate Limit: This setting specifically controls the number of new connection attempts per second. It is the correct tool for managing traffic spikes and protecting backend resources from being overwhelmed by a high frequency of new requests.

Comparison (Connection Limit): A standard Connection Limit (Option C) restricts the total concurrent connections allowed at any one time, regardless of how fast they arrive.

Other Profiles: OneConnect (Option A) is used for connection pooling and reuse to reduce server-side load, and HTTP Compression (Option B) reduces bandwidth usage but does not limit connection counts or rates.