Now that you are on or you have just started using VMware ESXi 6 and would like to do some monitoring via SNMP here is a way to enable this and set the community string in the process.
By default, remote clients are prevented from accessing services on host, unless configured to start automatically.
While you can simple set SNMP to start it does not set the community name and this is where we drop into the cli to do this.
Connect to the ESXi 6 host terminal or via SSH and issue the following commands:
esxcli system snmp set --communities public esxcli system snmp set --enable true
By doing the following you have set the community strong value and started the service.