Answered question

What does NL-Network-01 errors mean, and what can I do to troubleshoot the cause?

I have recorded a script, handled the dynamic parameters, and am ready to run a load test. Upon running a load test, I start to receive many NL-Network-01 errors instead of the actual server response. What could be the cause of my script failing to get the right server responses during my load test?

During a load test, many virtual users will run at the same time against your application and it will consume significant network resources.

Some network errors may happen in a scenario and one such error could be "NL-Network-01". NL-Network-01 errors can be represented differently, but they basically mean the same thing:


There was an issue to sending or receiving the response back from the server for a certain request.

By looking at the details (in the Results part, open the errors tab, select the error and look at the response content) of the NL-Network-01 error, you can get info about what happened during the failed response. They generally show one of two things:

a) " No route to host: connect" error probably indicates that an incorrect network interface has been used. Or there is some issue with routing to a server from the Load Generator.

b) " Connection reset" error may occur when the target server or a network device is overloaded. This sometimes can manifest as a Connection timeout: read timeout

With the NoRouteToHostException error, you can check the load generator's advanced network settings to ensure the right network interface is being used.


With the SocketException: Connection reset/timeout error, this can be an indication of a server overloaded or some network device between the LG and application server.

If all your User Load is getting this error, especially if the LG's are not in the same location in the network, then most likely the issue might be the server, or some resource the server uses, like a database server.

If only some of the User Load is getting this error at one time, it might indicate some network device that is overloaded or misconfigured, like a router or switch.

Try to compare the times during the test where the errors are concentrated, and compare that with logs from the server or network device(s).

Sometimes a network capture is needed, or some debugging turned on to gather more info on another test, if it can be reproduced.

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