You are assigned a project to configure SRX Series devices to allow connections to your webservers. The webservers have a private IP address, and the…

This scenario requires two distinct Network Address Translation (NAT) functions. First, to allow external users on the Internet to access the internal webservers, the SRX device must translate the public destination IP address of incoming packets to the private IP address of the webserver. This function is Destination NAT.

Second, for the webservers to initiate their own connections to the Internet (e.g., for updates), their private source IP address must be translated into a public IP address. This function is Source NAT. The requirement that this public IP be different from the one used for inbound access is a configuration detail within source and destination NAT rules, but the fundamental types required are source and destination NAT.

A. static NAT: This is a method of NAT that creates a one-to-one mapping. While it can be used for destination NAT, "Destination NAT" is the more precise term for the function of translating the destination address, which is the core requirement.

B. hairpin NAT: This is used when an internal host needs to access another internal host using its public IP address. This scenario is not described in the question, which focuses on Internet-to-private and private-to-Internet traffic flows.

1. Juniper Networks TechLibrary

"NAT Overview for SRX Series Devices": This document defines the primary NAT types. It states

"Destination NAT is used to translate the destination IP address of a packet entering a private network... Source NAT is used to translate the source IP address of a packet leaving a private network." This directly maps to the two requirements in the question.

URL: https://www.juniper.net/documentation/us/en/software/junos/nat/topics/concept/nat-overview-for-srx-series-devices.html

2. Juniper Networks TechLibrary

"Understanding Network Address Translation (NAT)": This guide further clarifies the roles. "With destination NAT

the security device translates the destination IP address of a packet entering the private network from a public IP address to a private IP address." and "With source NAT

the security device translates the source IP address of a packet leaving the private network to a public IP address."

URL: https://www.juniper.net/documentation/us/en/software/junos/nat/topics/concept/nat-understanding.html