Network 

planning and constructing of networks:
- local area network (LAN),
- wireless LAN (WLAN),
- wide area network (Internet/WAN),
- virtual private network (VPN)

security of networks against outside attacks, e.g.:
Viruses, Trojans, Worms, Hackers
configuration of Firewalls (Watchguard, Cisco, a.s.o.)