Links and filenames are correct as of the last update of this write-up. Netgate may remove legacy versions without notice for security reasons.
Get-FileHash .\pfSense-CE-2.5.1-RELEASE-amd64.iso.gz pfsense 251 download iso link
For legacy testing, you might also find older ISOs listed under the pfSense-CE directories on pkg.freebsd.org or files.netgate.com/mirror/downloads/ , but the direct link above remains the most reliable. Links and filenames are correct as of the
After downloading, check the SHA256 checksum: pfsense 251 download iso link
: Provides a direct link to the compressed ISO file: pfSense-CE-2.5.1-RELEASE-amd64.iso.gz .