Lower MTU on tun Device for OpenVPN Client | Network Manager in Debian and Ubuntu defaults to an MTU of 1500 for an openvpn tun interface. This caused me grief when tethering via T-Mobile and using openvpn. To make sure your openvpn connection works properly, you will need to adjust the MTU lower. Here is how!
pfSense – Free Open Source Firewall | pfSense is an excellent customization of FreeBSD for use either as a firewall or a router. FreeBSD is known for powering many commercial and large enterprise firewall appliances. pfSense gives you that same extensive feature set in a version you can install yourself on your own hardware or purchase pre-installed by many vendors. pfSense is