Operating System: Microsoft Windows (all version) Linux Red-Hat, SuSe, CentOS, Ubuntu, Debian, Gentoo, Slackware Telephony: Asterisk, Asterisk NOW, Elastix, VCdial, 3CX, FreePBX Open Source Technology Installation, Configuration and administration: PFSense, Zeroshell, MySQL, Apache2, PHP5, Asterisk, Openvpn, VPN Hardware: PABX, Routers, L3 Switches, Mikrotik