Admins Handbook

Enable SSH access on ESX host
Install vmware vSphere CLI

Go to:
C:\Program Files (x86)\VMware\VMware vSphere CLI\bin

See configuration with:
vicfg-snmp.pl –server 10.0.0.42 -s

Setup snmp:
vicfg-snmp.pl –server 10.0.0.42 -c info -p 161 -t 10.0.0.10@161/public,10.0.0.17@161/public
CIM:
vicfg-snmp -server 10.0.0.42 -y indications

IPMI:
vicfg-snmp -server 10.0.0.42 -y sensors

10.0.0.42 — esx host
161 – port (udp)
10.0.0.10/10.0.0.17 target (HP SIM etc.)
info – my community string

Enable snmp
vicfg-snmp.pl –server 10.0.0.42 -E

Se configuration agin.
vicfg-snmp.pl –server 10.0.0.42 -s

test with snmpwalk:
SnmpWalk.exe -r:10.0.0.42 -c:info

Update:
On a ESXi5.1 and newer, use esxcfg-snmp.pl isted of vicfg-snmp.pl