[Solved] GNS3 Error - 206 Unable to create UDP NIO

In this article, I am going to tell you how to resolve the 206 UDP error. I was so irritated to see this "206 Unable to create UDP NIO" error while trying to open any saved topology. The error looks like below,

I went through a lot of forums to trace out the root cause of this issue. I found the solution, we will discuss about this post.  I happened to receive this error on Windows 8 machine & this could occur in any platform. Follow the below steps to solve the same.

Changing UDP Port Number

First try to change the UDP port number to a new value as shown below. Here, I have changed to 10001 from 10000.

This might help you to open your topology file. But for me changing udp port number also did not help.

These port numbers might be used by some other application in your PC. 

Editing topology file

The UDP port number in GNS3 Preference tab should be same as your topology file configuration. For example, if you have configured 10001 as your Base UDP in GNS3 tool, your topology file also should have the same value.

The below images illustrate the output of netstat -an command in command prompt. You can see that 10000 UDP port is used by some application, hence i have changed it to 10001 manually in my configuration file and in GNS3.

After doing the above steps, I guess you will be able to open your LAB in GNS3 without any problem. If you have any other doubts please post in comment box.