Device Gigabit Interface & its sub-interface utilization don't add up in Spectrum

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Article ID: 242142

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Updated On:

Products

CA Spectrum DX NetOps CA Performance Management - Usage and Administration

Issue/Introduction

Observed that Gigabit interface max utilization crossing near 1Gbps. But, its sub-interfaces utilization is not going above 2% (20Mbps).

How is this possible, shouldn't the sub-interface utilization add up to the total utilization of the parent interface?

Cause

This issue is caused by the MIB data sent back from the device. This can be identified by running a MIB walk on it via sapwalk2.

Environment

DX NetOps CAPM Release : 20.2 or later

Resolution

Take the following example device data and look through it to find the indexes of interfaces that exhibit this issue:

# grep "Ethernet1/5" sapwalk.out 

1.3.6.1.2.1.2.2.1.2.436224000 , OctetString , Ethernet1/5

1.3.6.1.2.1.2.2.1.2.436227001 , OctetString , Ethernet1/5.3001

1.3.6.1.2.1.2.2.1.2.436227002 , OctetString , Ethernet1/5.3002

So the parent interface Ethernet1/5 has an Index of 436224000.

The sub-interface Ethernet1/5.3001 has an index of 436227001.

And the other sub-interface' Ethernet1/5.3002 index is 436227002.

The metric equation for Bits/In is:

(CalculatedSpeedIn > 20000000 && isdef(ifHCInOctets) && ifHCInOctets > 0) ? (ifHCInOctets*8) : (ifInOctets <= maxOctets20Mbps ? (ifInOctets*8) : null)

Since the speed is greater than 20000000, it uses the ifHCInOctets OID whose field number is 1.3.6.1.2.1.31.1.1.1.6.

Searching for this OID in the MIB data for each of the 3 indexes of the interfaces:

grep "1.3.6.1.2.1.31.1.1.1.6" sapwalk.out | grep 436227002

1.3.6.1.2.1.31.1.1.1.6.436227002, Counter64   , 0

For sub-interface Ethernet1/5.3002, it has a value of 0 for ifHCInOctets. Same for the other sub-interface:

grep "1.3.6.1.2.1.31.1.1.1.6" sapwalk.out | grep 436227001

1.3.6.1.2.1.31.1.1.1.6.436227001, Counter64   , 0

However, when you look at the parent interface, it has a significant value:

grep "1.3.6.1.2.1.31.1.1.1.6" sapwalk.out | grep 436224000

1.3.6.1.2.1.31.1.1.1.6.436224000, Counter64   , 10717544238782

If the Bits/In (ifHCInOctets) value for the parent was the sum of the two sub-interfaces, then they should have non-zero values that add up to the value in the parent (10717544238782). But they clearly don't, so this is a configuration issue on the device side.

Check with the device owner to see if they've configured the sub-interfaces to correctly report their values to the SNMP agent of the device.