[Solution] GNS3 could not connect | Gns3 common errors

Saifudheen SidheeqGns3, Latest PostsLeave a Comment

It’s common in gns3 that you end up getting the error messages now and then when you are working on different topologies. Moreover, it frustrates us when we cannot find a way around to fix it.
In this article, I am going to cover some of the error messages that I have received. Also, how I have troubleshot them. Below are the ones that I have covered.

"Error while creating link: Internal server error" Error while creating link: Internal server error

I was trying to create a topology in GNS3, where I had to add VM’s from both the local server and the gns3VM server to the gns3 topology. However, whenever I try to attach the interface, I get below error message

Internal server error
Error while creating link: Internal server error

Reason for Gns3 error while creating link: internal server error.

I was using the host binding address as my laptop loopback adapter which is, This is cool, if you are using either local machine as server or gns3 VM as the server, however if you wanted to use both then you need to make sure both the local server and the gns3vm are in the same network and able to communicate to each other.

gns3 host binding

Since both the local server and the GNS3 had to communicate for the topologies to work, I needed to change host binding from loopback adapter to VMware adapter to which gns3 has connected.

Gns3 had the IP address of, and the vnet1 where the GNS3 had connected to has the IP address of, I changed the host binding to to expect things would work just fine.

changing host binding address

However, it didn’t work either this time and started to throw a different error message in the gns3 console

WaitForConnectionWorker thread stopping with an error: Could not connect to on port 3080: timed out
Could not connect to on port 3080: timed out

Troubleshooting Gns3 Could not connect to on port 3080: timed out

At the same time, the error “Could not connect to on port 3080: timed out”  showed up on gns3 GUI as well.

Could not connect to on port 3080: timed out

I was thinking about what’s going on. Then I realized that I had McAfee endpoint security installed on my system, which could be blocking this connection.

I went to the firewall section of the McAfee endpoint security and started to look for the logs related to the error that I am getting.

Eventually, I found the below log, which says block traffic from the IP which is my gns3 network from the GNS3 software

Time:  09/21/2019 11:28:35 PM
Event:  Traffic
IP Address:
Message:      Blocked Incoming TCP  – Source :  (63066) Destination :  (3080)
Matched Rule:  Block all traffic

Now we found the root cause its just a matter of allowing the traffic in the firewall for the gns3 to communicate. 

There are two ways to resolve the issue.

The first one is to disable the firewall which I don’t want to, and some of you would have a machine that was given by your company, and it doesn’t allow you to turn off the firewall due to lack of admin rights.

The second and safer option is to allow this specific traffic in the firewall.

To allow this specific traffic in McAfee Endpoint Security, you would have to create a rule and apply it. If you are using a company laptop, then you would have to get in touch with your IT to get this done for you.

Step1. Open McAfee Endpoint Security and click on the firewall section. Then it would open up the firewall management section.

McAfee Endpoint Security firewall

Step2. Scroll down to the Rules section and click on Add rule.

McAfee Endpoint Security firewall add rules

Step 3. Give it a name and select the direction to apply to ‘Either’ not just in or out.

McAfee Endpoint Security firewall add rules, name and direction

Step 4. Leave everything default and click Add under specify networks. In add network window Type the name of the network add the subnet you wanted to allow for the gns3 to work.

firewall allow local and remote subnet for gns3

In my case, the IP address is, and the mask is 24. Hence I allowed for both remote and local network and clicked OK

Step5. Click Apply on the main screen.

McAfee Endpoint Security firewall apply rules

Step 6. Reopen the GNS3, and you will no longer get those error messages, plus you can add devices from local server and gns3vm as well to your network topology.

[Solved] GNS3 could not connect |  Internal server error

Internal server error Unable to start VMware VM

I also had one issue when I added Ubuntu Vmware VM to the gns3, and whenever I try to start the VM it starts to throw below error message, and the VM would never start.

Internal server error

Here is the way to fix this issue,

  1. go to edit preferences in gns3
  2. Click on VMware
  3. Click on Advanced local settings and keeping the interface value minimum to vnet2 to vnet6 and click on Configure, once it’s done, try adding the VM and start again. It would be good to go.