Netreo detects bandwidth using SNMP. Specifically, we read the ifSpeed and/or the ifHighSpeed MIB.
ifHighSpeed is only supported on devices set to SNMPv2 polling, and reports only in megabits (not fractions), so in order to avoid rounding off the bandwidth on low-speed ports, all interfaces with a reported speed below 1Gbps (1,000,000,000 bits/second) use the ifSpeed MIB exclusively.
If we detect that it’s a serial interface, we do allow a certain amount of bursting over 100%. However, this doesn’t change the “maximum” used to calculate percentages – that is always strictly based on the bandwidth setting.
If the interface is more than 56Kbps, but less than 1.5Mbps, we assume it could burst as high as 1.5Mbps.
If the interface is over 1.5Mbps, but less than 45Mbps, we assume it might be a fractional T3 and allow bursts up to 45Mbps.
If the interface is more than 45Mbps but less than 155Mbps, we assume it might be a fractional OC3 and allow bursts up to 155Mbps.