Which setting should be configured to prevent source NAT of the client IP in the back-end connection?

Question

Options

• AConnection Multiplexing in the Application Profile
• BX-Forwarded-For HTTP Header in the HTTP Application Profile
• CPreserve Client IP in the Application Profile
• DProxy Protocol in the L4 Application Profile

• A
  2% (1)
• B
  4% (2)
• C
  89% (48)
• D
  6% (3)

Explanation

Preserve Client IP (option C) directly instructs the load balancer to disable source NAT on the back-end connection, causing the real client IP to be forwarded to the server rather than replaced with the load balancer's IP - exactly what the question asks.

• A (Connection Multiplexing) pools and reuses back-end TCP connections for efficiency, but doesn't address how the source IP is handled.
• B (X-Forwarded-For) inserts the original client IP into an HTTP header, which is useful for logging, but the back-end still sees the load balancer's IP as the TCP source - NAT still occurs.
• D (Proxy Protocol) prepends client connection metadata to the TCP stream (similar concept to XFF but at L4), but it does not prevent source NAT either; it just gives the back-end a way to read the original IP from the payload.

Memory tip: "Preserve" = "protect the original" - if you want the client IP preserved (unchanged) all the way to the server, use Preserve Client IP. XFF and Proxy Protocol are workarounds around NAT, not prevention of it.

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