Get all mib
% snmpwalk -v 2c -c public localhost > all_mib.txt

View all_mib.txt and find to need mib value

Example
In all_mib.txt FILE
HOST-RESOURCES-MIB::hrProcessorLoad.768 = INTEGER: 1

% snmpwalk -v 2c -c public localhost hrProcessorLoad.768

Total CPU idle in Linux (Using net-snmp)
% snmpwalk -v 2c -c public localhost 1.3.6.1.4.1.2021.11.11.0