Strange

I have configrd check_ifutil on debian jessie 8.5…it gives output of ethernet on locally but in nagios…update the old value very very slow…like…if eth tx:450KBps..and server traffic increases to 50MBps/sec…then this plugin return…only 5MBps…until i have to manually run the script on server then nagios update its value to 50MBps….plz solve this