What tool we use in network moniter system nd how to use it?

I will recommend to use HP IMC (Intelligent Management Center).  Only you need to configure SNMP on devices. HP IMC will monitor everything. Even it shows the network topology and can run automated backups. Generates logs and give voice alerts.Also supports many other features including Nettwork Bandwidth usage, Very easy for Wireless Tshooting. HP IMC is also Supported for Cisco Gears. Configuration makes easy with HP IMC. You can try the demo version which lasts for60 -90 days.