https://rayka-co.com/lesson/juniper-srx-source-nat-interface/
Juniper SRX Source NAT allows users with a private IP address within the network to communicate over the Internet.
This is possible when private source IP addresses are translated to a public address when traffic is routed from an internal network to the Internet.
The source private IP address can be translated to the outgoing interface IP address which will be discussed in this section. It can also be translated into an IP address from a pool of IP addresses, which is discussed in the next section.