Firewall-to-firewall Link

A setup, typically referred to as a Site-to-Site VPN , is a secure connection that allows two separate local networks in different locations to communicate safely over an untrusted public network like the internet. Core Concept

What is Firewall Configuration and Why is it Important? - Fortinet Firewall-to-Firewall

This architecture establishes a "virtual tunnel" where each network's firewall acts as the gateway. Instead of individual computers connecting to a server, the firewalls themselves negotiate a secure link to bridge the two entire sites together. A setup, typically referred to as a Site-to-Site