Official distribution has shifted toward the Netgate Installer , which requires a Netgate Store account to download installation media. Netgate typically discourages using older versions like 2.5.1 due to security vulnerabilities and outdated software. Technical Overview: pfSense 2.5.1
To recap the direct answer to your query—the is officially hosted at Netgate’s file repository. Use the direct path provided in Part 2 of this article. You must extract the .gz archive and write it using raw DD mode. pfsense 251 download iso link
: Provides a direct link to the compressed ISO file: pfSense-CE-2.5.1-RELEASE-amd64.iso.gz . pfsense 251 download iso link
Before we dive into the download and installation process, let's take a look at some of the key features and improvements in pfSense 2.5.1: pfsense 251 download iso link