I have worked for 5 years as a full time Linux/Unix Administrator, in businesses like ISPs and Mobile Telephony Providers and i have worked with implementation, administration and manteniance of the following systems (Linux) :- PPPoE authentication system, including RADIUS server, Database Server and web management software.Web based Interface integration and monitoring system for each client.Configuration of Cisco and Mikrotik Routers as PPPoE Servers.Gardenwall server, providing client accounting info.- Corporate Mail Server based on Axigen.- Web Servers, including Web Hosting Services.- Main DNS Servers.- Proxy Servers (SQUID) including Cisco Routers configuration based on WccP and virtualization with xen.- Monitoring Server based on Cacti- Firewalls based on IPCoP and SmoothWall- Internal IM server (Openfire)- Game Servers (Counter Strike)- VPN services based on IPSec and SSL- Intrusion Detection System based on SNORTOther duties:- Server tuning for MySQL based Database Servers.- I