Prometheus based on snmp to monitor network equipment considerations

1. Use ifHCOUTOctetsinstead ifOUTOctets, the former is a 64-bit counter and the latter is a 32-bit counter
2. In the configuration file of snmp-exporter, you can walk whatever oid is captured, minimize the walk and improve efficiency
3. The alarm indicator usually uses the port occupancy rate instead of the absolute value of ifSpeedthe port traffic. The value of the GB port is 1000, which is decimal, and the unit is megabits, for example

rate(ifHCOUTOctets{job='snmp',ifOperStatus='1'}[2m]) * 8 / (ifSpeed{ifOperStatus="1"} * 1000000) * 100 >= 90 <= 100

4. Both the uplink and downlink bandwidth of the full duplex port are ifSpeed