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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?

Environment

DX NetOps CAPM Release : 20.2 or later

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.

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.