When i monitor a snmp value with MRTG it all works fine. When the device that is beeing monitored goes offline mrtg just takes the last value and draws a flat graph. Does anyone know how to prevent this?
I believe the options would be:
The manual states:
Log unknown data as zero instead of the default behaviour of repeating the last value seen. Be careful with this, often a flat line in the graph is much more obvious than a line at 0.
Normally we ignore all values which are zero when calculating the average transfer rate on a line. If this is not desirable use this option.