F5-CTS-LTM BIG-IP Local Traffic Manager Practice Test 2 — 15 Questions

Question 1

An LTM expert is troubleshooting a scenario where persistent traffic is failing to reach the same pool member. Which TWO factors should the expert investigate as potential causes for persistence failure?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The persistence profile timeout is set to a value shorter than the client's session duration.. Persistence ensures that a client's subsequent requests are handled by the same server. When this fails, it is often due to misconfiguration of the persistence profile or environmental factors like source NAT. Investigating the profile type and the persistence timeout is critical because mismatched configurations or premature expiration of table entries will result in the client being load balanced to a different server member unexpectedly.

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The pool members are located in different data centers.

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The virtual server is using the 'Round Robin' load balancing algorithm.

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The VLAN associated with the pool member is disabled.

Question 2

An LTM administrator needs to configure a virtual server to handle both HTTP and HTTPS traffic using a single VIP. What is the most effective way to achieve this on a BIG-IP?

Accepted Answer

Use a single virtual server with a wildcard port configuration.. To handle both protocols on one virtual server, the administrator can utilize an iRule or a Local Traffic Policy to inspect the incoming traffic. If the traffic is plain HTTP, it can be redirected to HTTPS. By using a single VIP with a 'Performance (L4)' or standard profile, the administrator can ensure consistent security policies and simplified configuration management across the entire application delivery chain.

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Create two separate virtual servers, one for port 80 and one for port 443.

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Enable 'Port Translation' on the virtual server.

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Configure the virtual server with 'Address Translation' disabled.

Question 3

What is the primary function of the 'Default Persistence Profile' in a virtual server configuration?

Accepted Answer

It provides a fallback mechanism for session stickiness.. The default persistence profile determines how the BIG-IP tracks client sessions if no specific persistence logic is defined or if the initial connection needs a fallback method. It ensures that, in the absence of more specific application-layer cookies or headers, the system maintains consistent server selection based on common criteria like the client's source IP, preventing disruption in services that require session continuity.

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It defines the health monitor behavior for all pool members.

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It dictates the load balancing algorithm for the pool.

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It encrypts the communication between the BIG-IP and the server.

Question 4

An LTM administrator needs to ensure that client SSL connections are terminated at the BIG-IP, but the original client IP address must be preserved for the backend web servers. Which configuration approach should the administrator implement?

Accepted Answer

Apply an HTTP profile with 'Insert X-Forwarded-For' enabled to the virtual server.. To preserve client IP addresses while performing SSL termination, the BIG-IP must insert an X-Forwarded-For header into the HTTP request header before forwarding it to the pool member. This is achieved by attaching an HTTP profile with the 'Insert X-Forwarded-For' option enabled to the virtual server. This ensures that backend applications can identify the true source of the traffic despite the SNAT or proxy nature of the BIG-IP.

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Enable Source Address Translation (SNAT) Automap on the virtual server.

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Configure a FastL4 profile with the 'Loose Initiation' setting enabled.

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Use a OneConnect profile to multiplex client connections to the backend.

Question 5

Refer to the exhibit. The administrator notices that the pool members are marked as 'down' despite being reachable. What is the most likely cause based on the provided configuration?

Accepted Answer

The pool monitor lacks a 'send' string specifying the Host header.. The pool is configured with a basic 'http' monitor. By default, the HTTP monitor requires a specific URI to check, and if none is provided, it defaults to GET / with no host header. If the backend web server is configured for virtual hosting, it will reject the request without a valid Host header, causing the health check to fail and marking the member as down.

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The virtual server is missing a SNAT pool definition.

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The TCP profile is incompatible with the pool member IP addresses.

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The virtual server lacks an iRule to handle the traffic.

Question 6

Which TWO of the following statements regarding BIG-IP Local Traffic Manager (LTM) persistence profiles are correct?

Accepted Answer

Cookie persistence requires an HTTP profile to be associated with the virtual server.. Persistence ensures that a client's subsequent requests are sent to the same server in a pool. Source Address Affinity persistence uses the client's IP to track sessions, while Cookie persistence uses application-level cookies. Understanding the difference is vital for stateful applications, as IP-based persistence can fail behind NAT devices or proxies, whereas cookie-based persistence provides better granularity for individual browser sessions.

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Source Address Affinity persistence is the best choice for web applications requiring high-granularity session tracking.

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Source Address Affinity persistence can effectively handle sessions even if the client IP changes frequently.

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Cookie persistence is hardware-accelerated and consumes no CPU resources.

Question 7

An LTM administrator is configuring a new virtual server and wants to limit the number of concurrent connections per client IP to prevent potential resource exhaustion. Which feature should be used?

Accepted Answer

Virtual Server Connection Limits.. The Rate Class and Connection Limit features in BIG-IP LTM allow for granular control over traffic volume. Specifically, using the 'Connection Limit' setting on a pool member or the 'Rate Class' object applied to a virtual server allows for shaping and restricting traffic. These controls are essential in protecting backend infrastructure from distributed denial-of-service attacks or misconfigured client applications that might generate excessive concurrent connections.

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iRules with the 'drop' command based on client IP headers.

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TCP Profile 'Idle Timeout' settings.

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SNAT Pool IP address rotation.

Question 8

Which BIG-IP feature should be utilized to perform traffic redirection based on the content of an HTTP request, such as switching pools based on the requested URL?

Accepted Answer

iRules. iRules are the standard, highly flexible scripting language provided by F5 to manipulate traffic. They allow administrators to inspect request data, such as headers, cookies, or URI paths, and make real-time decisions, including selecting a different pool. This capability is essential for modern applications where a single virtual server may need to support multiple services or route traffic based on complex business logic.

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Local Traffic Policy

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Persistence Profiles

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SNAT Pool

Question 9

Which TWO factors contribute to the determination of a pool member's state when using a custom health monitor? (Choose TWO)

Accepted Answer

The configured timeout value of the monitor.. Health monitors on BIG-IP LTM track the availability of backend resources. The state is determined by the combination of the monitor's response to the probe and the configured interval/timeout settings. Understanding these factors is vital for LTM specialists to tune detection sensitivity, preventing unnecessary flapping of pool members while ensuring that unhealthy servers are removed from the rotation promptly to maintain high availability and accurate load balancing decisions.

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The number of active connections to the pool.

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The persistence profile assigned to the virtual server.

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The priority group activation threshold.

Question 10

Which THREE conditions must be met for a virtual server to successfully process traffic? (Choose THREE)

Accepted Answer

The virtual server must be enabled.. A virtual server requires a valid combination of configuration objects to process traffic. These include a listener IP/port, an associated pool (or iRule logic), and active, healthy pool members. Understanding these prerequisites is fundamental for troubleshooting connectivity issues in BIG-IP environments, as any missing component will result in dropped traffic or connection resets by the LTM device before the request reaches the backend infrastructure.

Answer

A default pool must be assigned.

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The virtual server must have a default persistence profile.

Question 11

An administrator wants to log all traffic hitting a specific virtual server. Which feature should be used?

Accepted Answer

High-Speed Logging (HSL).. High-speed logging (HSL) is the recommended method for logging traffic at scale on BIG-IP. By using an iRule combined with an HSL destination and publisher, administrators can export logs to an external syslog server. This approach is highly performant and does not degrade the control plane, making it critical for monitoring production traffic without impacting the BIG-IP device's overall load handling capabilities.

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Local syslog files.

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TCPDump.

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iRule 'log' command.

Question 12

What is the primary function of an iRule 'LB_SELECTED' event?

Accepted Answer

To intercept the server selection.. The 'LB_SELECTED' event triggers immediately after the BIG-IP has made a load balancing decision but before the connection is actually established with the chosen pool member. This is the ideal point in the traffic flow to perform actions such as logging the chosen server, modifying the connection parameters, or performing advanced diagnostic tasks related to the server selection process, which is highly useful for troubleshooting complex load balancing logic.

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To terminate the client connection.

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To modify the HTTP response body.

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To decrypt the client SSL handshake.

Question 13

An LTM administrator needs to ensure that client SSL sessions are terminated at the BIG-IP, but the original client IP address must be preserved for the backend web servers. Which configuration approach should the administrator implement?

Accepted Answer

Apply an HTTP profile to the virtual server with the 'Insert X-Forwarded-For' option enabled.. Inserting an X-Forwarded-For header is the industry standard for maintaining client identity in Layer 7 environments. Since SSL termination occurs at the BIG-IP, the backend server only sees the BIG-IP self-IP as the source. By using an HTTP profile to insert this header, the application can read the real client IP, ensuring accurate logging, geo-location, and security policy enforcement without breaking the encrypted transit between client and F5.

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Enable SNAT Automap on the virtual server and use a custom iRule to rewrite the TCP header.

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Configure the virtual server to use a FastL4 profile with source address persistence.

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Disable SNAT on the virtual server and ensure the BIG-IP is the default gateway for the backend servers.

Question 14

Refer to the exhibit. Users report that they are being redirected to the fallback host even when the backend servers are healthy. What is the most likely cause of this behavior?

Accepted Answer

The pool members are failing the health check monitor.. The fallback-host parameter in an HTTP profile redirects traffic when the pool members are unavailable. If traffic is hitting this host while members are healthy, it suggests that the monitor assigned to the pool is incorrectly reporting members as down or the HTTP response codes returned by the servers do not match the expected criteria, triggering the profile's failover mechanism despite the physical connectivity being established.

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The HTTP profile is missing a rewrite header configuration.

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The virtual server is missing a SNAT configuration.

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The fallback-host requires a specific iRule to function.

Question 15

An administrator needs to distribute traffic based on the content of an HTTP request header, specifically the 'User-Agent'. Which F5 feature is the most efficient and scalable way to achieve this?

Accepted Answer

Implement a Local Traffic Policy with a rule condition matching the 'User-Agent' header.. Local Traffic Policies are designed to handle content-based switching with higher performance than traditional iRules. By using the 'switch' logic within a Policy, the BIG-IP evaluates rules in a declarative manner, which is optimized by the underlying TMOS architecture. This approach is highly efficient for inspecting headers and directing traffic to different pools based on specific string matches within the request.

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Use a complex iRule with a 'switch -glob' statement.

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Configure an HTTP Class profile to redirect based on header content.

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Use persistence profiles to track the 'User-Agent' string.