Server - PRTG Network Monitor Tool

PRTG Network Monitor here is an interesting monitoring tool that give you the ability to monitor Server (free up to 100 devices)

Network monitoring:

• More than 200 sensor types covering all aspects of network monitoring
• Uptime/Downtime Monitoring
• Bandwidth Monitoring using SNMP, WMI, NetFlow, sFlow, jFlow, Packet Sniffing
• Application Monitoring
• Virtual Server Monitoring
• SLA monitoring
• QoS Monitoring (e.g. when using VoIP)
• Environmental Monitoring
• LAN, WAN, VPN, and Multiple Site Monitoring
• Extensive event logging
• IPv6 support
• Agent-less monitoring (optional agents (remote probes) allow monitoring for even deeper metrics)

http://www.it.paessler.com/