Problem I have come to expect vague error messages that seemingly blame the network. This one is no different. Server Error in ‘/’ Application. The network path was not found Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.ComponentModel.Win32Exception: The network path was not found

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Several hundred users lost network connectivity. They went down randomly, one by one, and over a short period of time. Some users had intermittent connectivity. All of the network devices were online and functional. Users were roaming the halls and getting bored. This called for a packet capture, but with clients offline it had to be done on a network switch. In this instance, the capture was performed at the distribution switch on the layer 3 VLAN.

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While the general rule of thumb is to capture at the client, or at least start there, sometimes it’s necessary to take captures at both ends of a connection. The client perspective will allow you to view the problem as it is seen from the client. The server perspective might show the same thing. Or, in some cases like this one, it will provide the reason for the problem. The problem was that a webpage wouldn’t load.

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*Disclaimer: all captures in this post were anonymized using TraceWrangler. I was recently asked to help with a performance issue. I was informed a transfer was going to take weeks instead of a couple days as expected. The transfer rate was getting 80Mbps throughput max on a 10Gbps connection. So, I setup captures at both ends and got to work. This is just a quick summary of that work with the classic tell-tale signs of a performance problem.

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Chris Sereno

For 11 years networking was my profession with a specialized focus on proactive and reactive performance analysis. More recently I have embraced the AWS platform. This blog reflects my experience both past and present.

AWS Architect at Caterpillar, Inc.

US