VoIP – Asterisk(FreePBX, Elastix), CUCM/CUCME,
Routers – Cisco 2900/3900/etc
Switch – Cisco 2960/3750/etc, Dlink, HP, AT
Firewall – Cisco ASA, FWSM
Wireless – Mikrotik, Motorola Canopy, etc
OS – Linux/FreeBSD
PL – C,Perl,Bash,...
DBMS – MySQL,PostgreSQL