Practice Free F5CAB3 BIG-IP Administration Data Plane Configuration (F5CAB3) exam Exam Questions Answers With Explanation

To provide encrypted communication between users and a virtual server, the BIG-IP system acts as a transparent SSL/TLS proxy. The administrative configuration required for this is a Client SSL profile.

When multiple hostnames (FQDNs) are associated with a single IP address, the system must determine which SSL certificate to present to the client during the initial TLS handshake. This is achieved using an extension of the TLS protocol called Server Name Indication (SNI).

The configuration logic is as follows:

Profile Type: The Client SSL profile is responsible for terminating the SSL connection from the client (the user) to the BIG-IP system.

The Setting: Within the Client SSL profile (under the "Advanced" view), there is a field specifically called Server Name. By entering the specific hostname (e.g., www.example.com) in this field, the BIG-IP system can match the hostname requested by the client in the ClientHello message to the correct profile.

Implementation: The administrator typically creates multiple Client SSL profiles—one for each hostname—and assigns them all to the same virtual server. One of these profiles must be designated as the Default SSL Profile for SNI to handle requests where the client does not provide a hostname or provides one that does not match any specific profile.

By using the Client SSL profile and the Server Name setting, the BIG-IP system ensures that each user receives the correct certificate for the specific site they are trying to reach, even though all sites share a single virtual server IP.

From the exhibit, the pool contains different applications on different service ports (for example, HTTP/80, FTP/21, HTTPS/443, SSH/22). To mark pool members correctly, BIG-IP must be able to verify the actual service running on each member’s port.

In BIG-IP Administration: Data Plane Configuration, monitor behavior is described as follows:

When multiple monitors are assigned to a pool, the Availability Requirement controls how monitor results are evaluated:

At least one = the pool member is marked up if any one of the assigned monitors succeeds.

All = the pool member is marked up only if every assigned monitor succeeds.

For pools containing members with different services/ports, using All can incorrectly mark members down because monitors intended for other services will fail on the wrong port.

Why C is correct:

Assigning HTTPS, HTTP, FTP, and SSH covers the actual services shown in the pool.

Setting the Availability Requirement to at least one ensures that each pool member is considered available when its appropriate service monitor succeeds, without being forced to pass unrelated service monitors.

Why the other options are incorrect:

A / D (Availability Requirement = all): would cause members to be marked down when unrelated monitors fail (e.g., SSH monitor against an HTTP member).

B (includes ICMP): ICMP can indicate the host is reachable even if the application service is down, which does not “accurately” reflect service availability.

Therefore, the best choice is HTTPS, HTTP, FTP, and SSH with Availability Requirement of at least one health monitor.

Performance (Layer 4) virtual servers rely on FastL4 profiles to provide high-speed L4 processing without full proxy overhead.

Below is BATCH 2 (next 10 questions) extracted only from your uploaded document that are clearly related to BIG-IP Administration: Data Plane Configuration topics.

?As requested, I have strictly excluded questions related to:

Licensing

HA / Device Trust / Sync-only

Logging destinations

User roles

Hardware, EUD, support processes

System-only administration

Source: Your uploaded TMOS Administration v2.0 document

A red diamond indicates that the Virtual Server is enabled but unavailable, typically due to all pool members being down.

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.

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.

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

This scenario describes a classic case of asymmetric routing in a "one-arm" or non-gateway deployment. When a BIG-IP system is configured for SSL offloading, the following traffic flow occurs:

Client-Side: The client establishes a successful SSL/TLS handshake with the Virtual Server. This explains why the user can "successfully establish an SSL connection."

Server-Side: The BIG-IP decrypts the traffic and forwards it as plain HTTP to the backend server. The packet trace confirms the server receives the HTTP GET request and responds with the content.

The Routing Failure: By default, the BIG-IP system preserves the client's original source IP address. If the backend server's default gateway is not the BIG-IP system (or if the server is on the same subnet as the client), the server will attempt to send the response directly back to the client's IP address, bypassing the BIG-IP.

Stateful Drop: Because the BIG-IP is a Full Proxy, it expects the response to return through its own internal state table to be encrypted and sent back to the client. Since the response bypasses the BIG-IP, the BIG-IP connection eventually times out, and the client receives no data despite the server having sent it.

Solution (SNAT): Enabling Secure Network Address Translation (SNAT), specifically SNAT Auto Map, ensures that the BIG-IP replaces the client's source IP with its own internal self-IP before sending the request to the server. This forces the server to send the response back to the BIG-IP, allowing the BIG-IP to complete the transaction and deliver the content to the user.