To use mrtg-ping-probe you need to configure MRTG to call it from within the definition of a target host.
This is done in the MRTG config file, which is usually /etc/mrtg.conf.
Here's an example snippet: change the target name and IP address to suit your needs.
Target[your.target.ping]: `/usr/bin/mrtg-ping-probe 123.456.789.123`
SetEnv[your.target.ping]: MRTG_INT_IP="123.456.789.123" MRTG_INT_DESCR="ping"
MaxBytes[your.target.ping]: 100
AbsMax[your.target.ping]: 200
Options[your.target.ping]: gauge, growright
YLegend[your.target.ping]: ping time (ms)
ShortLegend[your.target.ping]: ms
Legend1[your.target.ping]: Maximum Round Trip Time in ms
Legend2[your.target.ping]: Minimum Round Trip Time in ms
Legend3[your.target.ping]: Maximal 5 Minute Maximum Round Trip Time in ms
Legend4[your.target.ping]: Maximal 5 Minute Minimum Round Trip Time in ms
LegendI[your.target.ping]: Max:
LegendO[your.target.ping]: Min:
Pay close attention to the backticks in the first line which tell MRTG to execute the nominated external
program. Note also that you need to use the "gauge" option, since the results of subsequent ping probes
are independant values and not an incrementing counter.