Persistent Sysctl Tuning

This host will route traffic and handle many open files, so two kernel parameters need to be set — persistently (a drop-in under /etc/sysctl.d/, not just a live sysctl -w that's lost on reboot):

net.ipv4.ip_forward = 1 # enable IPv4 forwarding (routing)

fs.file-max = 100000 # raise the system-wide max open files

Write both into a file under /etc/sysctl.d/ (e.g. 99-tuning.conf). Grading reads the sysctl config the way sysctl --system does; a live-only change won't persist and won't pass.