Vce F5CAB3 Questions Latest

A 400 Bad Request response from an HTTP/1.1 web server is a definitive indicator that the HTTP request sent by the health monitor is missing a required Host header . In HTTP/1.1, the Host header is mandatory per RFC 7230. Web servers — particularly those hosting named virtual hosts such as — will reject any HTTP/1.1 request that omits the Host header, returning a 400 error, which the BIG-IP monitor interprets as a failed health check, marking all members DOWN.

The correct Send string must include:

The GET request line with HTTP/1.1 protocol declaration

A \r\n (carriage return + line feed) after the request line

The Host: www.f5.com header to satisfy HTTP/1.1 requirements

A \r\n after the Host header

Connection: Close header to instruct the server to close the connection after responding

A final \r\n\r\n to properly terminate the HTTP request headers

Only option C satisfies all these requirements with the correct syntax and Host header inclusion.

Option D (the current configured string) omits the Host header entirely — the root cause of the 400 error. Options A and B are structurally incomplete or syntactically malformed.

When clients connect through a single source IP (NAT) — such as a corporate proxy or carrier-grade NAT — Source Address Affinity persistence becomes entirely ineffective because all clients share an identical source IP address. This would force every client session to the same pool member, completely eliminating even distribution and defeating the purpose of load balancing.

Cookie Persistence is the optimal solution in this scenario because it operates at Layer 7 , inserting a unique cookie into each client ' s HTTP/HTTPS response. Each individual browser session carries its own distinct cookie value, allowing the BIG-IP to identify and persist individual clients to specific pool members — regardless of whether they share a common source IP address. This guarantees both session persistence and even load distribution across pool members.

The remaining options are unsuitable because:

Destination Address Affinity persists based on destination IP, irrelevant for client-to-server session stickiness.

SSL Persistence uses the SSL Session ID for persistence, but SSL session IDs are frequently renegotiated and are unreliable for long-term persistence across modern TLS implementations.

Source Address Affinity fails entirely under NAT conditions as described.

Cookie persistence is the industry-standard method for HTTPS application load balancing requiring per-client session affinity.

To solve this requirement, we must distinguish between the two " legs " of an SSL connection in a BIG-IP environment: Client-side and Server-side.

Current State (SSL Bridging): The administrator states the servers currently require encrypted traffic. This means the BIG-IP is likely performing " SSL Bridging. " In this setup, a Client SSL profile terminates encryption from the user, and a Server SSL profile re-encrypts the traffic before sending it to the back-end servers.

Target State (SSL Offloading): The requirement is to " offload SSL " to reduce web server load. This means the BIG-IP will continue to handle the encryption for the users (keeping the Client SSL profile) but will communicate with the back-end servers using unencrypted HTTP.

Why Option A is correct:

Remove the Server SSL profile: By removing this profile, the BIG-IP stops attempting to initiate an SSL/TLS handshake with the pool members.

Configure Pool Members to use HTTP: The service port for the pool members must be changed (typically from port 443 to port 80) so that the BIG-IP sends standard HTTP traffic to the servers.

Why other options are incorrect:

B & D: These suggest removing the Client SSL profile. If you remove this, the users can no longer connect via HTTPS, which violates the requirement for encrypted communication between the users and the BIG-IP.

C: Changing the Virtual Server to accept HTTP traffic would mean the user-to-BIG-IP connection is no longer encrypted, which is the opposite of SSL termination/offloading.

Similar to the logic required for managing multi-service backend environments, the issue described—where servers hosting multiple protocols like FTP and HTTP are experiencing uneven distribution—stems from the BIG-IP ' s default behavior of treating each pool independently. If the administrator uses a member-based load balancing method, the BIG-IP distributes HTTP traffic regardless of how much FTP traffic that same physical server is currently processing.

To resolve this, the administrator must utilize the Least Connections (Node) method. By switching both the HTTP and FTP pools to this algorithm, the BIG-IP begins to make load balancing decisions based on the total combined connection count for the IP address of each server. When a new HTTP request arrives, the BIG-IP checks which server has the fewest total connections (including existing FTP sessions). This prevents a server that is already busy with long-lived FTP transfers from being overwhelmed by a sudden burst of HTTP requests.

Ratio methods (Options A and C) are static and rely on the administrator manually assigning weights to servers based on their perceived capacity; they do not adapt to real-time fluctuations in traffic volume across different pools. Least Connections (Member) (Option B) remains blind to the " cross-pool " traffic on the same hardware. Only the Node-based Least Connections approach provides the global visibility necessary to " even out " the total resource utilization across servers supporting multiple distinct applications.