F5CAB3 F5 BIG-IP Administration Data Plane Configuration (F5CAB3) exam Free Practice Exam Questions (2026 Updated)

The pool member list in the exhibit shows servers listening on four distinct service ports: 80 (HTTP), 21 (FTP), 443 (HTTPS), and 22 (SSH). To accurately monitor a pool where members provide different services, the administrator must apply monitors that correspond to each of those specific services.

The key to this configuration is the Availability Requirement (also known as "Monitor Rule"). If the administrator sets the requirement to "All health monitors," every single monitor (HTTP, HTTPS, FTP, and SSH) must pass for a member to be marked "Up." This would cause an immediate failure: for example, a server listening only on port 80 would fail the HTTPS, FTP, and SSH checks, resulting in the member being marked "Down" even if the HTTP service is healthy.

To ensure accuracy, the administrator should apply all four relevant monitors and set the Availability Requirement to at least one monitor. With this setting, the BIG-IP marks a member as "Up" if any of the assigned monitors return a successful response. Therefore, the member at 10.200.50.210:80 will stay "Up" as long as the HTTP monitor passes, even though it fails the FTP, HTTPS, and SSH monitors. This configuration allows a single pool to contain diverse service types while ensuring that the specific port defined for each member is verified correctly. Option C is incorrect because ICMP only checks if the IP is alive, not if the specific service port is functioning.

In a BIG-IP environment, a Fallback Persistence Profile is utilized as a secondary "stickiness" mechanism when the primary (Default) persistence method fails to provide a valid persistence record. For example, if a Virtual Server uses HTTP Cookie Persistence as its primary method, but a client’s browser has cookies disabled, the BIG-IP will be unable to find a persistence cookie in the request. Without a fallback method, the system would treat every request from that client as a new, independent connection, potentially breaking the application session.

Source Address Affinity (also known as Source Address Persistence) is the most common and standard choice for a fallback profile. It operates at the network layer (Layer 3) by tracking the client’s source IP address. Because every IP packet contains a source address, this method is virtually guaranteed to work even when application-layer data (like Cookies or SSL Session IDs) is missing or encrypted beyond the BIG-IP's visibility. While Universal (Option A) and Hash (Option D) profiles are highly flexible and can use iRules to persist on almost any data, they require specific configuration and logic that may not always be present or valid. SSL persistence (Option C) relies on the SSL Session ID, which frequently changes due to modern browser security practices (session renegotiation), making it less reliable than Source Address Affinity. By configuring Source Address Affinity as the fallback, the administrator ensures that the BIG-IP has a "safety net" to maintain session integrity based on the client's IP address when the more granular cookie-based persistence is unavailable.

Fallback persistence is used when the primary persistence method fails. Source Address Affinity is a Layer 4 persistence method and is fully supported as a fallback option for most virtual server types.

The configuration provided utilizes Priority Group Activation in conjunction with the min_active_members setting. Priority groups allow an administrator to define primary servers and "backup" servers within the same pool. The BIG-IP prioritizes traffic based on the assigned priority number, with the highest number receiving traffic first.

In this specific configuration, the priority 3 group is the primary group. Therefore, connections are first distributed to all pool members with priority 3 as long as they are available. The system will continue to use only the priority 3 group unless the number of available members in that group falls below the min_active_members value, which is set to 2.

If the priority 3 group has fewer than two active members, the BIG-IP "activates" the next available priority group (priority 2) and distributes traffic among the remaining members of priority 3 and all members of priority 2. This cascading logic continues down the list. Consequently, if both the priority 3 group and the priority 2 group have fewer than two members available, traffic is directed to the priority 1 group. This ensures that even in a multi-server failure scenario, the system has a last-resort group of servers to handle the traffic.

Option D is incorrect because if only one member of priority 3 goes down, there are still two members active (10.12.10.8 and 10.12.10.9). Since 2 is not less than the min_active_members threshold of 2, the priority 2 group will not yet be activated. Option B is incorrect because traffic flows from high priority to low priority, not the other way around.

This scenario requires unequal load distribution based on server capacity. The newer servers must receive more connections than the older ones, while still dynamically accounting for active connection counts.

According to BIG-IP Administration: Data Plane Configuration documentation:

Weighted Least Connections (member) combines:

Connection awareness (least connections)

Administrator-defined weights (ratios) to reflect server capacity

Pool members with higher weights receive proportionally more new connections than members with lower weights, even when using the same load balancing algorithm.

Why B is correct:

Allows assigning higher weights to newer servers and lower weights to older servers

Ensures smarter traffic distribution based on both capacity and real-time load

Why the other options are incorrect:

A. Global AvailabilityUsed for disaster recovery and site failover, not intra-pool load distribution.

C. Round RobinDistributes connections evenly without considering server capacity.

D. Least Connections (member)Balances only by current connection count and does not account for differences in server performance or capacity.

Correct Resolution:

Use Weighted Least Connections (member) and assign higher weights to newer servers so they receive more traffic while protecting older servers from overload.

When the connection limit is reached, BIG-IP resets new connections, even if pool members are healthy.

When multiple users share one source IP, source-address persistence fails. Cookie persistence uniquely identifies users at Layer 7 and ensures correct session handling.

SSH is a TCP-based service. A TCP monitor validates service availability without requiring application-layer inspection.

A Performance (Layer 4) virtual server does not inspect or process application-layer data such as HTTP headers or cookies. Therefore, only Layer 4–compatible persistence methods can be used.

According to the BIG-IP Administration: Data Plane Configuration documentation:

Source Address Affinity persistence operates at Layer 4 and uses the client IP address to maintain session persistence.

It is fully compatible with Performance (Layer 4) virtual servers.

It works regardless of encryption, making it suitable for TLS-secured applications.

Why the other options are incorrect:

B. Cookie persistenceRequires an HTTP profile and Layer 7 inspection, which is not supported on Performance virtual servers.

C. Microsoft RDP persistenceIs protocol-specific and not applicable to web-based TLS traffic.

D. Host persistenceRequires HTTP host header inspection, which is not available at Layer 4.

Correct Resolution:

Source Address Affinity persistence is the appropriate choice for maintaining persistence on a Performance (Layer 4) virtual server handling TLS traffic.

Below is Batch 1 (Questions 1–10) extracted only from your uploaded document that are directly related to BIG-IP Administration: Data Plane Configuration topics (Virtual Servers, Pools, Load Balancing, Monitors, Persistence, SNAT, Profiles).

I have excluded system-only, licensing, support, hardware, HA management-only, and admin UI questions that are not Data Plane–focused.

Source: Your uploaded TMOS Administration v2.0 document

✅ BATCH 1 (10 Questions)

X-Forwarded-For inserts the original client IP into HTTP headers while SNAT is enabled.

The log message “Intercept exhaustion” indicates that the BIG-IP system has exhausted the available source port translations for one or more SNAT addresses. This occurs when too many concurrent client connections are being translated through a limited number of SNAT IP addresses, and all ephemeral source ports (typically ~64,000 per SNAT IP) are in use.

According to the BIG-IP Administration: Data Plane Configuration documentation:

Each SNAT IP address provides a finite number of available source ports.

When the number of concurrent connections exceeds the available port space, the BIG-IP logs an Intercept exhaustion error and new connections fail.

The recommended resolution is to increase the available SNAT resources by adding additional IP addresses to the SNAT pool.

Why the other options are incorrect:

A. Increase the timeout of the SNAT addressesIncreasing timeouts may actually worsen the problem by keeping ports allocated longer, accelerating port exhaustion.

B. Remove the SNAT pool and apply SNAT AutomapSNAT Automap uses the Self IP addresses on the egress VLAN, which may not provide additional capacity and can introduce routing or design issues. This is not a direct or recommended fix for SNAT exhaustion.

C. Remove an IP address from the SNAT poolThis would reduce the number of available source ports and further exacerbate the intercept exhaustion condition.

Correct Resolution:

By adding an IP address to the SNAT pool, the BIG-IP increases the total number of available source ports, alleviating intercept exhaustion and restoring successful client connections.

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.

URI-based traffic steering requires inspection of the HTTP request. BIG-IP processes HTTP headers and URIs in the HTTP_REQUEST event. Pool member selection based on URI must occur before the request is sent to the server, making HTTP_REQUEST the correct event.

The X-Forwarded-For header preserves the original client IP when SNAT is enabled.

By default, BIG-IP load balancing algorithms (such as Round Robin) distribute connections evenly across all available pool members. However, persistence profiles override normal load balancing decisions by forcing subsequent connections from a client to be sent to the same pool member.

According to the BIG-IP Administration: Data Plane Configuration documentation:

Persistence creates a client-to-server mapping that is honored before load balancing algorithms are applied.

When persistence is enabled, BIG-IP may repeatedly select the same pool member even if others are available.

This directly alters load balancing behavior.

Why the other options are incorrect:

A. Adding a OneConnect profileOneConnect optimizes server-side TCP connections but does not change which pool member is selected.

B. Enabling SNAT automapSNAT affects source address translation, not pool member selection.

C. Enabling a fallback host in the HTTP profileA fallback host is only used when no pool members are available.

Correct Resolution:

Adding a persistence profile alters load balancing behavior by maintaining client affinity to a specific pool member.

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. Via the GUI at the Resources tab for the virtual serverThe Resources tab in the Configuration Utility displays all traffic-handling objects applied to the Virtual Server, including assigned iRules. This is the primary GUI location to verify whether an iRule is influencing data plane traffic.

C. Via TMSH with the list /ltm virtual commandThis TMSH command displays the full Virtual Server configuration, including any iRules listed under the rules section. It is the authoritative CLI method to confirm iRule usage.

Why the other options are incorrect:

A. Via TMSH with the list /ltm rule commandThis command only shows the contents of an iRule and does not indicate whether the iRule is attached to or used by any Virtual Server.

D. Via the GUI at the iRule tab for the virtual serverBIG-IP does not provide a dedicated “iRule” tab on Virtual Servers. iRules are viewed and managed under the Resources tab.

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.

SSH is a Layer 4 TCP-based protocol that operates on TCP port 22 and does not use HTTP in any capacity. In the exhibit, the Virtual Server is configured with an HTTP Profile applied, which is inappropriate for SSH traffic and causes connection failures.

According to the BIG-IP Administration: Data Plane Configuration documentation:

An HTTP profile must only be applied to Virtual Servers handling HTTP or HTTPS traffic.

When an HTTP profile is attached, BIG-IP expects HTTP headers and attempts to parse application-layer data.

Non-HTTP protocols such as SSH, FTP (control), SMTP, and other raw TCP services will fail if an HTTP profile is enabled.

Why the other options are incorrect:

A. Set Protocol to UDPSSH uses TCP, not UDP. Changing the protocol would break SSH entirely.

B. Set Source Address to 10.1.1.2The source address setting controls client access restrictions and is unrelated to protocol parsing issues.

C. Set Destination Address/Mask to 0.0.0.0/0The destination address is already valid for a specific SSH service and does not impact protocol handling.

Correct Resolution:

The BIG-IP Administrator should remove the HTTP Profile (set it to None) so the Virtual Server functions as a pure Layer 4 TCP service, allowing SSH connections to pass through successfully.

The BIG-IP system uses a centralized management framework to ensure that all devices within a Sync-Failover group share a consistent configuration. When an administrator makes a change on any member of the group—whether it is the active or the standby device—the system detects a "ConfigSync" mismatch. The "Device Management >> Overview" screen tracks these changes by comparing the commit ID and timestamps of the configurations across all peers.

If a change is made on the standby member, that device now possesses a more recent configuration than the other members of the group. Consequently, the BIG-IP GUI will display a status of "Changes Pending" and suggest a Recommended Action to resolve the discrepancy. In this scenario, the correct action is to Synchronize the standby member configuration to the group. This push operation will copy the updated configuration from the standby device to the active device (and any other peers), bringing the entire cluster back into a "In Sync" status. It is important to note that BIG-IP allows bi-directional synchronization; you do not have to be on the active device to push a configuration. However, administrators must be cautious: choosing Option C (Synchronizing the active member to the group) would overwrite the changes just made on the standby device with the older configuration from the active device, effectively reverting the changes. The Recommended Action always points toward the direction that propagates the most recent change to the rest of the group.

The exhibit shows the advanced configuration of a VLAN where the Fail-safe option is checked. VLAN Fail-safe is a high-availability feature used to monitor network connectivity on a specific VLAN. When enabled, the BIG-IP system monitors the VLAN for network traffic. If the system does not detect any "useful" traffic on the VLAN within the specified Fail-safe Timeout (which is 90 seconds in the exhibit), it attempts to generate traffic by pinging the default gateway or other devices. If it still detects no traffic, the BIG-IP concludes that the VLAN is unreachable or the network interface has failed, and it triggers a "Fail-safe Action"—in this case, "Reboot" or a failover to the peer device in the HA group.

Because the administrator has just created a new VLAN that "does NOT yet have any traffic," the Fail-safe mechanism triggers immediately after the 90-second timeout period. Since no devices are yet communicating on this VLAN, the BIG-IP incorrectly assumes there is a hardware or cabling failure and forces a failover to ensure the standby device (which might have better connectivity) takes over. To prevent this unwanted failover, the administrator should uncheck the Fail-safe box for that specific VLAN until the VLAN is fully populated with active nodes and regular traffic. Once the application is live and traffic is flowing, Fail-safe can be re-enabled to provide an additional layer of redundancy. Auto Last Hop (Option A) and Source Check (Option B) are routing and security features that do not trigger HA failover events.