Cicada (started as Chupacabra) is a lightweight network monitoring with auto-discovery tool and alerting.
Supported protocols: ICMP (ping), SNMP v1/2c/3, Modbus TCP, IPMI, WMI and http (plain-text, json, xml).
Also you can polling Check-MK, Munin and Zabbix agents and check TCP/UDP ports.
Cross-platform, open source, extendable, free.
Multi-protocol device polling
Live network diagrams
Grouping devices and metrics by tags
Check threshold values of metrics
Templates to create device copy in one click
Auto-discovery metrics by predefined rules
Device bulk import
Extreme compact storage of history data (2-4Byte per numeric value)