ManageEngine OpManager - Monitors routers, switches, firewalls, load-balancers, wireless LAN controllers, servers, VMs, printers, storage devices, and everything that has an IP and is connected to the network.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Cisco Data Center Network Manager - Cisco Data Center Network Manager offers network management system (NMS) support for traditional or multiple-tenant LAN and SAN fabrics.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
DCImanager - DCImanager is a platform for managing physical equipment. Connect any physical equipment to a single platform. Use the platform to manage your servers, switches, PDU as well as physical and virtual networks.
Prometheus - An open-source systems monitoring and alerting toolkit.