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201 · Question #303

Assume a client's traffic is being processed only by a NAT; no SNAT or virtual server processing takes place. Also assume that the NAT definition specifies a NAT address and an origin address while al

The correct answer is A. The source address would not change, but the destination address would be translated to the origin. When a client initiates traffic to a BIG-IP configured with only a NAT (destination NAT), the BIG-IP translates the destination address from the public NAT address to the internal origin address, while the client's source address remains unchanged.

Section 2: Configure Load Balancing Features

Question

Assume a client's traffic is being processed only by a NAT; no SNAT or virtual server processing takes place. Also assume that the NAT definition specifies a NAT address and an origin address while all other settings are left at their defaults. If a client were to initiate traffic to the NAT address, what changes, if any, would take place when the BIG-IP processes such packets?

Options

  • AThe source address would not change, but the destination address would be translated to the origin
  • BThe destination address would not change, but the source address would be translated to the origin
  • CThe source address would not change, but the destination address would be translated to the NAT's
  • DThe destination address would not change, but the source address would be translated to the NAT's

How the community answered

(40 responses)
  • A
    73% (29)
  • B
    3% (1)
  • C
    8% (3)
  • D
    18% (7)

Why each option

When a client initiates traffic to a BIG-IP configured with only a NAT (destination NAT), the BIG-IP translates the destination address from the public NAT address to the internal origin address, while the client's source address remains unchanged.

AThe source address would not change, but the destination address would be translated to the originCorrect

A Destination NAT (often just called NAT in this context on BIG-IP) is designed to translate an external destination IP address (the NAT address) to an internal, real server IP address (the origin address). When a client sends traffic to the NAT address, the BIG-IP performs this destination address translation, while leaving the client's original source IP address intact as it passes through.

BThe destination address would not change, but the source address would be translated to the origin

This describes a source address translation (SNAT) scenario, which the question explicitly states is not taking place, and incorrectly implies translating the source to the origin address.

CThe source address would not change, but the destination address would be translated to the NAT's

The destination address is translated from the NAT address to the origin address (the internal server), not back to the NAT's own address.

DThe destination address would not change, but the source address would be translated to the NAT's

This describes a source address translation (SNAT) scenario, which is explicitly excluded by the question, and incorrectly implies translating the source to the NAT's own address.

Concept tested: BIG-IP Destination NAT (DNAT) packet flow

Source: https://techdocs.f5.com/en-us/bigip-15-0-0/big-ip-system-basic-configurations--virtual-servers-and-snats.html

Topics

#NAT#source address translation#destination address translation#origin address

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