3 Ways to Solve Azure VM Connectivity Issues

Basic Fixes

• Review your Firewall: Disable your firewall. Then try connecting. That might be enough to fix it, as firewalls sometimes interfere with how VMs connect to each other.
• Check Possible Problems with NSG or UDR: Use the “Network Watch IP Flow Verify” or “Connection Troubleshoot” tools to see if there are issues with Network Security Group (NSG) or User-Defined Route (UDR). If so, you’ll need to configure new inbound rules for the NSGs.
• Check SNAT: SNAT port exhaustion problems can cause connectivity issues on VMs. You’ll need to make a VIP on each VM and secure it with NSG or an access control list (ACL).

 

How to Fix Azure VM Connectivity Issues Between Two VMs

Arguably the most common of all Azure connectivity issues is when two VMs on the same virtual network can’t connect with one another. There are numerous potential causes of this, but these steps should resolve the issue:

Step 1: Download “TCping” to your VM.

Step 2: Launch Command Prompt.

Step 3: Use the following command: “tcping64.exe -t <destination VM address> 3389” to ping the location where you downloaded TCping. (Replace the “destination VM address” part with the name of the folder).

Step 4: If that worked, move to Step 5. Otherwise, check your “Inbound port rules” on each VM and ensure there aren’t any matching blocking rules that could interfere with the connection, then run the TCping check again.

Step 5: Run a Remote Desktop connection to your VM by going into Azure, clicking “Virtual Machines,” selecting the VM you’re trying to connect, and hitting the “Connect” button.

Step 6: Try a connection check through PowerShell and the Azure Network Watcher and review the response.

Step 7: The Hops section of your connection check should display the source or issues behind your connectivity problem. You can then identify and fix each issue, using Microsoft’s own table of recommended actions.

Step 8: Run the connectivity check one last time, once you’ve taken resolution steps, to confirm it’s all fixed.

How to Resolve Azure Connection Issues with Second Network Adapters

You may also struggle to connect to virtual machine Azure second adapters on the same network. Here’s how to resolve that:

Step 1: Go to whichever VM has the secondary adapter, and load up a Command Prompt on it.

Step 2: Run this command: “Route add 0.0.0.0 mask 0.0.0.0 -p <Gateway IP>” and replace the “Gateway IP” part with your secondary IP.

Step 3: Launch Route Print and then try to connect.

Step 4: If that didn’t work, verify your “Inbound port rules” for both adapters (first and second). Check there aren’t any matching blocking rules that could cause clashes or interfere with the connection.

Step 5: Run a connection check to the second adapter and then a secondary check across the full environment through the Azure Network Watcher.

Step 6: Check the “Hops” to see what’s wrong, and follow Microsoft’s recommended steps to resolve it.

Fix Azure VM Connectivity Issues to the Internet

Some VMs also just can’t connect to the internet for one reason or another. Here’s how to fix that:

Step 1: Go to the Resource Explorer.

Step 2: Find “Subscriptions” and open it, then locate which VM is having an issue.

Step 3: Click on “Microsoft Network,” then go to “Network Interfaces” and pick the problematic interface.

Step 4: Select “Read/Write,” then choose “Edit.”

Step 5: At this stage, you’ll notice the button in the top left changes from “Get” to “Put.” Select your interface and click on the “Put” button.

Step 6: Refresh and retry the connection.

Step 7: If issues persist, go into the Azure Network Watcher and launch a connection check. Review “Hops” to see what’s going on and take the next best steps according to Microsoft.