Blog
SNMP errors and timeouts, 32-bit and 64-bit counters, switch port errors: notes with real snmpget output from MikroTik and net-snmp devices.
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ifInOctets vs ifHCInOctets: when a 32-bit SNMP counter wraps
ifInOctets wraps in 34 s at 1 Gbit/s and 3.4 s at 10 Gbit/s. Real RouterOS output, the wrap arithmetic, 64-bit counters and reboot spikes.
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SNMP timeout with no response: what each cause looks like
snmpget and snmpwalk print Timeout: No Response for many causes. Real output from RouterOS, net-snmp and a switch with no SNMP agent, plus a checklist.
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SNMPv3 authentication failure, unknown user and usmStats counters
Fix SNMPv3 Authentication failure, Unknown user name and silent timeouts with real snmpget output and a table of the six usmStats counters.
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Switch port errors: ifInErrors, FCS errors and discards explained
ifInErrors, ifInDiscards and dot3StatsFCSErrors on a switch port: what each one counts and how two reads tell a live cable fault from an old total.