Load balancer not forwarding port

Mohammed Abdulrahman 6 Reputation points
2022-04-19T21:08:54.247+00:00

Basically I have a load balancer > NAT > NSG > VM. I allowed port 8000 from all sides LB, NSG and VM. Even when using the tool it says "It seems that your backend resources are responding on all configured ports".

However, once trying to connect to that port and even using online tools to check if that port is open. It shows it as not open even though I had copied the same way that SSH forwarding was enabled. Does anyone know why it fails on port 8000? Perhaps I missed a step or something?

This image shows the NSG attached to the VM, which I had allowed port 8000 and 22. This is only for a test environment.
f8UkB48.png

This image shows the VM allowing and having an application running on port 8000.
mi337SW.png

This image shows when trying to troubleshoot the Load Balancer with the port 8000 NAT rule it says that were no problems (this did take a long time)

pcnsbFl.png

The image below shows the NAT rules for the load balancer, one of these I am using for using a different port for SSHing to the virtual machine and it works fine. But the one for port 8000 doesn't work.

SoKZHjb.png

Checking with an external tool to check if the port is open and only the one I am using for SSH works but the one for 8000 doesn't.
LyIk6wD.png

Azure Virtual Machines
Azure Virtual Machines
An Azure service that is used to provision Windows and Linux virtual machines.
7,113 questions
Azure Load Balancer
Azure Load Balancer
An Azure service that delivers high availability and network performance to applications.
401 questions

2 answers

Sort by: Most helpful
Most helpful Newest Oldest
  1. Mohammed Abdulrahman 6 Reputation points
    2022-04-23T00:39:15.073+00:00

    This has been resolved, I thank everyone who took their time and helped me. The lesson learned here is to know which VM you are working on and especially when you are tired at 3 am in the morning. I was working on another virtual machine all along, after I figured that out the other configuration to that virtual machine except the NAT rule because I forgot about that. I gave up on this and I came back with a steady mind.

    Then I reviewed this screenshots again and my configuration on the NAT to see that I still had it on the wrong virtual machine. Now it works :).

    1 person found this answer helpful.
  2. Martin Tästensen 456 Reputation points
    2022-04-20T19:43:30.66+00:00

    Okay, i will try - but please bear in mind that I am in no way, shape or form a linux expert.

    But if i recall right, a linux (debian atleast) creates two different interfaces, a loopback interface which is 127.0.0.1 (itself) and a eth0 which is the internal IP address of the server (eg. 192.168.0.10)

    In your picture, it is open for port 22 on 0.0.0.0 which I would suspect being all interfaces, but the port 8000 is "only" for 127.0.0.1.

    Again, i'm not a linux expert, but could the issue be that the port is only listening on the loopback interface?

    194783-linux.jpg