Netgate does not officially support or maintain the 2.5.1 branch anymore.
: Netgate limits community and commercial support to current releases.
Since pfSense 2.5.1 is an older version (released April 2021), it is primarily available through the following sources: : pfSense-CE-2.5.1-RELEASE-amd64.iso (617.2 MB). Third-Party Community Mirrors : The Wiert Corner : pfSense-CE-2.5.1-RELEASE-amd64.iso.gz . pfsense 251 download iso link
In a change from earlier plans, Netgate confirmed that AES-NI (a set of hardware instructions for cryptography) is not required to run pfSense version 2.5.1. This significantly expands the range of older hardware on which pfSense can be installed.
: This version removed the kernel-level WireGuard implementation that was briefly included in 2.5.0. Netgate does not officially support or maintain the 2
Note: Netgate occasionally moves older, deprecated releases into cold storage. If the specific 2.5.1 ISO is unavailable on the public mirrors, installing the latest release is the recommended pathway. Verifying Your pfSense 2.5.1 Download
Once you are on the download page or in the store, you will typically choose between two formats for your hardware: Third-Party Community Mirrors : The Wiert Corner :
Once you have the verified ISO file, you need to write it to a bootable medium.
Ultimate Guide to the pfSense 2.5.1 ISO Download and Installation