For those running a small Windows-based network (one SNMP capable router and 1 - 3 servers), the following client-limited versions of commercial applications may be useful:
- PRTG for monitoring network and bandwidth usage using SNMP, packet sniffing or Netflow protocol. The freeware version is limited to a single sensor (try the 'Internet' port on your router).
- GFI Network Monitoring for monitoring raw server statistics (CPU, disk etc for Windows and some Linux distributions) and applications (SQL Server, IIS, Exchange and others). A full list of features is available. The freeware version is limited to 3 servers.