I use Nagios to monitor about 30 Cisco 2960 switches (check_snmp_load, check_snmp_int). I only check load and one or two backbone interfaces of every switch.
I get a lot of false positives caused by lack of an answer from devices. I suppose SNMP UDP packets get lost somewhere but I have not been able to troubleshoot it.
I checked sh int summary
on every switch and there is no information about dropped packets (IQD nor OQD).
The same Nagios instance monitors dozens of other devices (linux servers, iDRACs/iLOs, SAN switches, tape libraries etc.) and there is always everything alright with those.
The only difference in infrastructure connections between Nagios and 2960s / other devices is that 2960s are connected through quite old FC infrastructure. Is it possible it is a matter of these FC cables? How can I check it (without purchasing expensive network measurements)? I already used iperf but it did not show any problems.
What else can I do to troubleshoot this issue?
Update: My SNMP configuration on 2960s is quite simple:
#sh run | include snmp
snmp-server community commstr RO