This article explains why polling a 10GB interface with SNMP MIB object ifSpeed does not work. SNMP MIB object ifHighSpeed should be used instead.

Polling a 10GB interface with SNMP MIB object  ifSpeed does not give the expected result, as shown in the sample output below.

Next, poll the ifSpeed for SNMP interface index (ifIndex) 21 . The following output shows the result:

Checking other interfaces, with walk option, it can be seen that, for example, GE interfaces the expected result is displayed:

The reason for the result is that the SNMP MIB object ifSpeed is a 32 bit object and the value is presented in bits per second. Therefore, the maximum value that can be used is 2^32-1 or 4294967295, which is approximately 4.3 GB.

The reason for the result is that the SNMP MIB object ifSpeed is a 32 bit object and the value is presented in bits per second. Therefore, the maximum value that can be used is 2^32-1 or 4294967295, which is approximately 4.3 GB.

Instead the SNMP MIB object ifHighSpeed should be used, as shown here:

user@austria-re0> show snmp mib get ifHighSpeed.21 
ifHighSpeed.21 = 10000


The value ifHighSpeed is interpreted as megabits per second.

This OID can be walked from a network management station, or from the cli:

1.3.6.1.2.1.31.1.1.1.15

Example:

lab@Wicket> show snmp mib walk 1.3.6.1.2.1.31.1.1.1.15

The command show snmp mib walk ifName is another way to correlate the interface names and the SNMP ifIndex : 

Note that the numbers following ifName in the output above, are the same as the ifIndexs below:

• show snmp mib
• This OID tree represents the compiled SNMP MIB module IF-MIB and includes only high-level compiled information...