Free BIG-IP Administration Data Plane Configuration (F5CAB3) exam Practice Questions

In BIG-IP systems, iRules influence traffic only when they are attached to a Virtual Server. If application traffic is being sent to nodes or pool members that are not defined in the pool, this typically indicates that an iRule is overriding the default load-balancing behavior by explicitly selecting a pool or node.

According to BIG-IP Administration: Data Plane Configuration and official F5 guidance:

iRules are associated with Virtual Servers, not directly with pools or nodes.

To determine whether an iRule is actively affecting traffic, the administrator must inspect the Virtual Server configuration.

Explanation of the correct answers:

B.  

C.  

Why the other options are incorrect:

A.  

D.  

Correct Conclusion:

To verify whether an iRule is responsible for unexpected node selection, the BIG-IP Administrator must examine the Virtual Server configuration, either through the Resources tab in the GUI or by using TMSH to list the Virtual Server configuration.

The two load balancing methods that consider all connections between the BIG-IP and each backend node — not just connections to a specific pool member — are Least Connections (node) and Weighted Least Connections (node) .

The critical distinction here lies in the node-level scope of evaluation. A node represents the backend server ' s IP address, regardless of how many services or ports it may be serving. Therefore:

Least Connections (node) directs new connections to the node with the fewest total active connections across all services on that server, providing a holistic connection-count perspective.

Weighted Least Connections (node) operates identically but factors in an administrator-defined ratio weight, allowing servers with greater capacity to proportionally absorb more connections while still evaluating total node-level connection counts.

By contrast:

Ratio (member) distributes traffic based on a static weight ratio and does not dynamically evaluate current connection counts.

Round Robin distributes traffic sequentially in rotation, completely ignoring current connection states on any node or member.

The node-based methods are particularly valuable in environments where a single backend server hosts multiple pool members across different ports, ensuring the server ' s overall load — not just per-service load — governs balancing decisions.

HTTP Compression on a BIG-IP system is an optimization feature that reduces the size of HTTP responses sent to clients, thereby saving bandwidth and improving page load times for end-users. To implement this functionality on a Virtual Server, the system requires two specific profiles to work in tandem: an HTTP profile and a Compression profile.

The HTTP profile (Option E) is a prerequisite because compression is an application-layer (Layer 7) operation. The BIG-IP must be " HTTP-aware " to parse the incoming requests and outgoing responses. The HTTP profile allows the BIG-IP to inspect the Accept-Encoding header from the client (to see if the client supports gzip or deflate) and to modify the Content-Encoding and Vary headers in the server ' s response. Without the HTTP profile, the Virtual Server operates at Layer 4 (TCP) and sees the traffic only as an opaque stream of bytes, making compression impossible.

The Compression profile (Option B) contains the actual settings and engine for the task. It defines which content types should be compressed (e.g., text/html, application/javascript), the compression level, and the minimum content length required before compression is applied. While a Stream profile (Option D) is used for data replacement (search and replace) and SSL profiles (Option C) are used for encryption, they do not provide compression logic. By applying both the HTTP and Compression profiles, the BIG-IP can successfully intercept server responses, compress the payload according to the configured policy, and deliver the optimized data to the user, effectively offloading the CPU-intensive compression work from the backend web servers.