The Dangers of Network Instability

Businesses today rely on bandwidth-intensive and latency-sensitive enterprise applications such as VoIP, streaming media, CRM, ERP, PDM, or a multitude of SaaS applications such as Salesforce. They build internet-connected trading or partner networks, where any delays in transactions can ripple work stoppages and cost overruns throughout numerous organizations. Discovering the common causes of network instability, then, is paramount.


Whether a network serves one building, multiple campuses, or divisions across the globe, instability is usually caused by misconfiguration or unknown change. The dynamic nature of mobile and network access technologies today makes these issues less obvious and more insidious.

Entuity Event Management System alerting to duplex mismatch, a major cause of network instability.

The embedded Entuity Event Management System alerts to port duplex setting changes and to port inbound faults, the latter of which may indicate a duplex mismatch. This allows IT staff to proactively identify a common source of network problems.

Duplex Mismatch Brings Network Instability to Manufacturing Company


A surprisingly persistent and ubiquitous problem occurring in most networks is duplex mismatch between system NICs and their associated switch port. In more than 90% of the customer proof of concepts Entuity has completed, our network management solution has identified duplex mismatches that had gone unaddressed for weeks or months. The potential impact and ensuing cost is compounded since performance issues from a duplex mismatch often don’t show up under light load.  When the load increases and the users are pushing the service heavily, that’s when performance will be massively impacted — just when they need it most. With the majority of transactions being TCP-based, the retry mechanisms will eventually allow the transactions to succeed, albeit very slowly.


Identifying and correcting duplex mismatches is also not a one-time, “set and forget” task.  It’s an ongoing issue in today’s fluid and evolving enterprise infrastructure.


Take for example a high-tech manufacturing company that was performing maintenance on their corporate application servers. Their Microsoft Exchange server needed requisite updates of security patches, so the operations team scheduled down time for 3:00 AM on a Saturday to minimize impact on the user community. Patching and updating went without a hitch, the server rebooted successfully, and everyone went home happy.


Come Monday morning, however, the moods were not as light.  As the wave of business users sat down at 8:00 AM with their cup of coffee to check their email, the operations callcenter was flooded with the dreaded complaint, “the network is slow and Outlook says the connection to the Exchange server is lost!” Realizing that most problems come as a result of change, and that the security patches were the last change made to the server, operations staff quickly uninstalled them and rebooted (running without important security patches, which put the network at high risk). But even as the staff began to breath a sigh of relief, the calls kept coming in.


Five IT technicians were tasked with troubleshooting the problem while the user community waited. The final fix was to swap out the server with a spare and relegate the original server to off-hour file backup alone. That also didn’t work. What was wrong? It wasn’t until weeks later when they upgraded their open-source network monitoring tools for Entuity that were they able to immediately identify the true cause of this problem. Uniquely sensitive to duplex mismatch issues, Entuity alerted the network manager that the NIC reverted to halfduplex state during the server reboot, causing incompatibility with the switch. It wasn’t the security patch at all.


How Entuity Identifies Duplex Mismatches

The advanced Entuity Event Management System (EMS) and comprehensive reporting capabilities allow it identify duplex mismatches in multiple ways. First, if a port duplex setting changes, Entuity raises an event that indicates the change. Second, if the port duplex setting has not changed, Entuity can identify duplex mismatches through a Port Inbound Fault “Incident,” which may point to a possible duplex mismatch. (An Incident is a collection of events that help prevent event storms and add focus to situations that may impact business services.)

Finally, Entuity can identify mismatches using its embedded Report Builder. In the figure below, a tabular inventory report displays only those ports that were configured for half-duplex operation. Given that ports are usually configured for full-duplex operation, this may indicate duplex mismatches, and warrant further investigation.


Entuity inventory report showing ports configured for half duplex operation, which may indicate duplex mismatch, a common cause of network instability.

Entuity inventory report showing ports configured for half duplex operation, which may indicate duplex mismatch.


For one high-tech manufacturing company, hundreds of hours of IT time uninstalling patches, swapping out the server, and finally reinstalling the patches could have been saved if they had been using Entuity. Through an integrated EMS and deep, actionable reporting capabilities, Entuity ensures that organizations have the immediate insight they need to quickly find real cause of problems of network instability before disaster strikes.

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