Q. I have a custom SNMP probe that returns high round-trip time values for the probed devices. How is round-trip time calculated for SNMP probes?

A. The round-trip time (RTT) reported for SNMP probes is the round-trip time of the final exchange. For custom SNMP probes, this will be the time to request and respond to all the variables in your custom probe.

RTT is calculated by the time it takes for the last packet sent to come back. In a custom probe with several variables, we send one request for all the variables. The RTT is the sum of the time it takes to retrieve all the information. It is possible that one of the variables takes longer than the others to return the data. Setting maxvars = 1 tells InterMapper to send each request separately in a separate packet (for each variable), so it can decrease the RTT if the last variable queried isn’t the slow one.

Add the following section to your custom SNMP probe to force InterMapper to request each variable one at a time:

maxvars = "1"