IFTABLE_CACHE_TIMEOUT control how frequent update ifTable counter.
Net-SNMP v5.4,v5.5 IFTABLE_CACHE_TIMEOUT 15
Net-SNMP v5.6,v5.7 IFTABLE_CACHE_TIMEOUT 3
Newer version have shorter cache timeout, but if you want to monitor real-time traffic by second, 3 seconds still useless.
To change this value
Method 1:
snmpset -v2c -cpublic localhost .1.3.6.1.4.1.8072.1.5.3.1.2.1.3.6.1.2.1.2.2 i 1 # after snmpd start
Note: use override to set the value does NOT work.
ref. How to set the agent update or counter refresh interval on net-snmp
Method 2:
Get Net-SNMP source tar ball, change the value in agent/mibgroup/if-mib/ifTable/ifTable_data_access.h
./configure && make && make install
