Are you deploying this on or a virtual machine (ESXi, Proxmox, Hyper-V)?
Navigating to these official backend mirrors allows you to find the pfSense-CE-2.5.1-RELEASE-amd64.iso.gz file safely. 2. Trusted Community Architecture Repositories pfsense 251 download iso link
: Modified versions may lack stability, causing unexplainable network drops. Are you deploying this on or a virtual