I needed to Monitor My CentOS 6.4 Box, many monitoring software like Nagios, cacti and zabbix need SNMP enabled on system to be monitored.
so here you are
# yum install net-snmp-utils #
Once you have installed the SNMP you need to configure the public query access to box.
first backup the snmp.conf
# mv /etc/snmp/snmpd.conf /etc/snmp/snmpd.conf.back nano /etc/snmp/snmpd.conf #
past following in the file
rocommunity public syslocation "PDC, Peters DataCenter" syscontact some@email_address.ext
save the file and restart the snmpd and add snmpd to start automatically
# /etc/init.d/snmpd start chkconfig snmpd on #
You are done. now SNMP based monitoring software will be able to query your centos box.