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Home > Success Center > Network Performance Monitor (NPM) > NPM Documentation > NPM 12.4 Administrator Guide > Manage interfaces with NPM > Detect and predict possible duplex mismatches

Detect and predict possible duplex mismatches

Created by Caroline Juszczak, last modified by Magdalena.Markova on Nov 02, 2016

Views: 826 Votes: 0 Revisions: 4

One of the most common causes of performance issues on 10/100 or 100/1000 Mbit Ethernet links occurs when one port on the link operates at half-duplex while the other port operates at full-duplex.

  1. Log into the Orion Web Console.
  2. Go to the node details view for the parent node of the interface you want to check for duplex problems.
  3. Consult the Possible Duplex Mismatches resource. If there are no errors, the resource is hidden.

    The resource lists all duplex interfaces on the node, percentage of transmit and receive errors, the neighboring node and interface. If the neighboring interface or node is not monitored in SolarWinds NPM, the appropriate columns are empty.
    The last column displays the duplex mode issue - Mismatch, or Unknown.

Duplex Mismatch

To be able to detect duplex mismatches, your nodes need to meet the following requirements:

  • The nodes must be monitored by SolarWinds NPM.
  • The nodes must be in the up state during the discovery.
  • The nodes must support topology and be interconnected.
  • Duplex of both devices must be identified as Full or Half.

The resource shows all duplex mismatches, not only 100% duplex mismatches. These are reported on by the Duplex Mismatch alert.

Possible Duplex Mismatch

If at least one of the link interfaces has the duplex mode defined as half or full, the resource helps you identify possible mismatch.

Possible duplex mismatches are visible in the duplex mode column as the Unknown duplex mode. They are identified in the following cases:

  • If the switch port reports more than 0.5% receive or transmit errors.
  • If the switch port reports CRC errors.
  • If the switch port reports Late Collision errors.

How do I resolve mismatches?

To resolve a duplex mismatch, make sure your hardware is working, and unify the duplex mode configuration on neighboring interfaces.


The Possible Duplex Mismatches does not display on Node Details view

If the resource does not appear on the node details view, there might be a performance issue due to the amount of interfaces and topology connections. Check the following logs for the occurrence of mismatch information:



The Possible Duplex Mismatches resource does not display percentage of errors

Possible causes:

  • No statistical data for these interfaces.
  • A performance issue connected with getting statistic information for the resource.
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