• Nagios 27.1%

• Wireshark 20.7%

• htop 12.3%

• Zabbix 10.5%

• Other 8.6%*

• Zenoss 6.2%

• Munin 3.4%

• PC Monitor 2.8%

• New Relic 1.9%

• Opsview 1.2%

• SaltStack 1%

• NTM (Network Traffic Monitor) .7%

• xosview .7%

• Manage Engine .5%

• FlowViewer .3%

• Circonus .2%

• SysPeek .2%

*Under "Other", most write-ins went to Icinga and OpenNMS.