use Putty to connect to your host or use the ESXi console.
cd to vmware folder : cd /etc/vmware/
do and ls you will see your beast snmp.xml here
Edit the file using vi
you will see a single line. press i to enter the edit mode.
we need to change false to true and add Public between <communities></communities>
once happy with this, Press Esc and the :wq to save and quit.
we will have to restart the services.sh under /sbin/ folder with /sbin/services.sh restart
you should now be able to use any monitoring software to monitor your hosts.
source : http://vm-blog.info