F5 BIG-IP Administration Data Plane Configuration (F5CAB3) exam F5CAB3 Exam Dumps: Updated Questions & Answers (October 2026)

This question tests precise knowledge of both TMSH command syntax and BIG-IP object namespace hierarchy . Two critical distinctions must be correctly identified:

1. create vs. modify: Since the Trunk already exists and the administrator is adding interfaces to it, the correct verb is modify — not create . Using create on an existing object would either throw an error or attempt to overwrite the object entirely, neither of which is the desired outcome.

2. /sys vs. /net namespace: Trunk objects in BIG-IP reside within the /net namespace, which encompasses network-layer constructs including Trunks, VLANs, Self IPs, and Routes. The /sys namespace is reserved for system-level objects such as management settings, software, and licensing — it does not contain Trunk objects.

Therefore, the only syntactically and functionally correct command is:

tmsh modify /net trunk trunk_A interfaces add {1.3 1.4}

This command appends interfaces 1.3 and 1.4 to the existing trunk_A object without disrupting currently assigned interfaces, increasing aggregated bandwidth accordingly.

Options A and C use the incorrect /sys namespace, and options A and B incorrectly use the create verb for an existing object.

The configuration error is the HTTP Profile = http setting. The virtual server is intended to load balance SSH , which operates over TCP port 22 and is not an HTTP application protocol. The configured TCP protocol and TCP profile are therefore appropriate, but an HTTP profile should not be attached to this SSH virtual server.

F5 documentation states that an HTTP profile defines how BIG-IP manages HTTP traffic . The standard http profile operates in Reverse proxy mode by default and invokes BIG-IP ' s HTTP protocol processing. F5 separately documents Transparent HTTP proxy mode as the mode that can forward invalid HTTP traffic instead of dropping it. This distinction is important because an SSH protocol exchange is not syntactically valid HTTP traffic.

Setting HTTP Profile to None removes unnecessary Layer 7 HTTP parsing and leaves the virtual server handling the SSH connection through its TCP profile. The other changes are inappropriate: SSH requires TCP rather than UDP; the source address does not need to equal the virtual server ' s destination IP; and changing the destination to 0.0.0.0/0 is unrelated to the application-protocol mismatch.

Reference Topics: Local Traffic Profiles → HTTP Profiles , Proxy Mode , TCP profiles , Virtual Server profile assignment .

Comprehensive and Detailed Explanation From BIG-IP Administration Data Plane Configuration/Course Guide/topics:

The monitor is explicitly sending an HTTP/1.1 request. For HTTP/1.1, the request must contain a valid Host header identifying the intended virtual host. The configured monitor sends the URI and Connection: Close header but omits Host: www.f5.com. A web server using name-based virtual hosting can therefore reject the request with HTTP 400 Bad Request , which explains why every pool member is marked down.

F5 ' s official BIG-IP monitor documentation gives the HTTP/1.1 convention in the form " GET / HTTP/1.1\r\nHost: server.com\r\nConnection: close\r\n\r\n " .

Option A follows that required structure: the request line identifies HTTP/1.1, Host: www.f5.com selects the correct hosted site, Connection: Close requests connection termination after the response, and the final \r\n\r\n properly terminates the HTTP header section. F5 also specifies that when HTTP/1.0 or HTTP/1.1 is used, the monitor evaluates the HTTP status code; a non-200 response such as 400 causes the monitored resource to be considered unavailable.

Reference Topics: BIG-IP LTM Monitors Reference → HTTP Monitor Send String , HTTP/1.1 request formatting , pool-member health monitoring .

The virtual server is intended to process SSH traffic on TCP port 22 , but the exhibit shows that the standard http HTTP profile is assigned. This is the configuration error. An HTTP profile enables BIG-IP Layer 7 HTTP processing and is appropriate only when the virtual server is expected to process HTTP protocol traffic. F5 documentation defines its purpose directly: “An HTTP profile defines the way that you want the BIG-IP system to manage HTTP traffic.”

SSH is not HTTP. It is an independent application protocol transported over TCP , conventionally using port 22 . Therefore, an ordinary SSH load-balancing virtual server should retain the TCP protocol/profile while having HTTP Profile set to None . F5 ' s SSH virtual-server configuration guidance specifically uses service port 22 for SSH and does not require an HTTP profile.

Options B, C, and D do not address the fault. The destination address 10.1.1.2 correctly identifies the virtual server, while source 0.0.0.0/0 appropriately permits clients from any source. Changing the protocol to UDP would be incorrect because SSH requires TCP.

Reference Topics: Virtual Server configuration; HTTP profiles; TCP profiles; application-protocol profile assignment; SSH traffic handling.

SSH (Secure Shell) operates over TCP port 22 , making the TCP health monitor the appropriate and correct choice for monitoring pool members in an SSH pool. The TCP monitor establishes a basic Layer 4 connection to each pool member on the designated port, verifying that the server is reachable and actively accepting TCP connections. A successful three-way handshake confirms the pool member is available; a failure marks it down and removes it from load balancing rotation.

The remaining monitor types are inappropriate for this use case:

UDP monitor operates at Layer 4 but uses the connectionless UDP protocol, which is incompatible with SSH since SSH exclusively uses TCP as its transport.

HTTP monitor sends a Layer 7 GET request expecting an HTTP response — irrelevant for an SSH service that does not speak the HTTP protocol.

HTTPS monitor functions identically to HTTP but over TLS — again, completely misaligned with SSH traffic and port behaviour.

For application-specific SSH validation beyond basic TCP connectivity, an external monitor or custom monitor could be used; however, TCP remains the standard and correct built-in monitor for SSH pool verification within the BIG-IP platform.

In a default BIG-IP configuration, the system utilizes the Load Balancing Method (typically Round Robin) to distribute each new connection across available pool members. However, the introduction of a persistence profile fundamentally changes this behavior. Persistence (also known as " stickiness " ) ensures that once a client has been load balanced to a specific pool member, all subsequent requests from that same client during a defined session or timeout period are directed to that same member, bypassing the standard load balancing algorithm. This is critical for applications that maintain state, such as shopping carts or authenticated sessions, where moving a user to a different server would result in a loss of session data.

While other options affect traffic handling, they do not " alter " the fundamental load balancing decision in the same way. A OneConnect profile (Option A) optimizes connection management by pooling idle server-side connections; while it changes how connections are reused, the initial load balancing decision still follows the configured method. A fallback host (Option C) is only utilized when the primary pool is unavailable, and since the question states all pool members are online, it remains inactive. SNAT Automap (Option D) changes the source IP address of the packet as it exits the BIG-IP toward the server to ensure return traffic passes back through the ADC, but it does not dictate which server is chosen for the request. Therefore, the persistence profile is the primary configuration element that overrides the load balancing algorithm to maintain a client-to-server relationship.

To determine if an iRule is influencing traffic for a specific Virtual Server, the administrator must verify the association between the Virtual Server object and any applied scripts. In the BIG-IP Configuration Utility (GUI), this association is found under the Resources tab of the specific Virtual Server. While there is an " iRules " sub-menu under Local Traffic, checking the Virtual Server ' s Resources tab is the definitive way to see which specific rules are currently active and in what order they are being processed for that particular traffic flow.

From the Command Line Interface (CLI), the tmsh list /ltm virtual < virtual_server > command provides a full text-based output of the virtual server ' s configuration. If iRules are applied, they will appear within a " rules { ... } " block in the command output. This is more effective than Option A, which only lists the contents of the iRule itself but does not show if or where it is applied. Option C is a common misconception; while some versions of the GUI have reorganized menus, the standard location for managing the association of profiles, policies, and iRules to a Virtual Server remains the " Resources " section. By identifying the applied iRule, an administrator can then review the script logic—often containing commands like pool or node—to see if it is overriding the default pool selection based on specific HTTP headers, URI paths, or client IP addresses.

Slow Ramp Time prevents new pool members from receiving full traffic immediately, avoiding overload.

Application-level monitors ensure that only the affected service is marked down, not the entire node.

Standard DNS queries use UDP. Configuring the Virtual Server for TCP causes DNS traffic to fail.