Network virtual appliance issues in Azure


We recommend that you use the Azure Az PowerShell module to interact with Azure. See Install Azure PowerShell to get started. To learn how to migrate to the Az PowerShell module, see Migrate Azure PowerShell from AzureRM to Az.

You may experience VM or VPN connectivity issues and errors when using a third party Network Virtual Appliance (NVA) in Microsoft Azure. This article provides basic steps to help you validate basic Azure Platform requirements for NVA configurations.

Technical support for third-party NVAs and their integration with the Azure platform is provided by the NVA vendor.


If you have a connectivity or routing problem that involves an NVA, you should contact the vendor of the NVA directly.

If your Azure issue is not addressed in this article, visit the Azure forums on Microsoft Q & A and Stack Overflow. You can post your issue in these forums, or post to @AzureSupport on Twitter. You also can submit an Azure support request. To submit a support request, on the Azure support page, select Get support.

Checklist for troubleshooting with NVA vendor

  • Software updates for NVA VM software
  • Service Account setup and functionality
  • User-defined routes (UDRs) on virtual network subnets that direct traffic to NVA
  • UDRs on virtual network subnets that direct traffic from NVA
  • Routing tables and rules within the NVA (for example, from NIC1 to NIC2)
  • Tracing on NVA NICs to verify receiving and sending network traffic
  • When using a Standard SKU and Public IPs, there must be an NSG created and an explicit rule to allow the traffic to be routed to the NVA.

Basic troubleshooting steps

  • Check the basic configuration
  • Check NVA performance
  • Advanced network troubleshooting

Check the minimum configuration requirements for NVAs on Azure

Each NVA has basic configuration requirements to function correctly on Azure. The following section provides the steps to verify these basic configurations. For more information, contact the vendor of the NVA.

Check whether IP forwarding is enabled on NVA

Use Azure portal

  1. Locate the NVA resource in the Azure portal, select Networking, and then select the Network interface.
  2. On the Network interface page, select IP configuration.
  3. Make sure that IP forwarding is enabled.

Use PowerShell

  1. Open PowerShell and then sign in to your Azure account.

  2. Run the following command (replace the bracketed values with your information):

    Get-AzNetworkInterface -ResourceGroupName <ResourceGroupName> -Name <NicName>
  3. Check the EnableIPForwarding property.

  4. If IP forwarding is not enabled, run the following commands to enable it:

    $nic2 = Get-AzNetworkInterface -ResourceGroupName <ResourceGroupName> -Name <NicName>
    $nic2.EnableIPForwarding = 1
    Set-AzNetworkInterface -NetworkInterface $nic2
    Execute: $nic2 #and check for an expected output:
    EnableIPForwarding   : True
    NetworkSecurityGroup : null

Check for NSG when using Standard SKU Public IP When using a Standard SKU and Public IPs, there must be an NSG created and an explicit rule to allow the traffic to the NVA.

Check whether the traffic can be routed to the NVA

  1. On Azure portal, open Network Watcher, select Next Hop.
  2. Specify a VM that is configured to redirect the traffic to the NVA, and a destination IP address at which to view the next hop.
  3. If the NVA is not listed as the next hop, check and update the Azure route tables.

Check whether the traffic can reach the NVA

  1. In Azure portal, open Network Watcher, and then select IP Flow Verify.
  2. Specify the VM and the IP address of the NVA, and then check whether the traffic is blocked by any Network security groups (NSG).
  3. If there is an NSG rule that blocks the traffic, locate the NSG in effective security rules and then update it to allow traffic to pass. Then run IP Flow Verify again and use Connection troubleshoot to test TCP communications from VM to your internal or external IP address.

Check whether NVA and VMs are listening for expected traffic

  1. Connect to the NVA by using RDP or SSH, and then run following command:

    For Windows:

    netstat -an

    For Linux:

    netstat -an | grep -i listen
  2. If you don't see the TCP port that's used by the NVA software that's listed in the results you must configure the application on the NVA and VM to listen and respond to traffic that reaches those ports. Contact the NVA vendor for assistance as needed.

Check NVA Performance

Validate VM CPU

If CPU usage gets close to 100 percent, you may experience issues that affect network packet drops. Your VM reports average CPU for a specific time span in the Azure portal. During a CPU spike, investigate which process on the guest VM is causing the high CPU, and mitigate it, if possible. You may also have to resize the VM to a larger SKU size or, for virtual machine scale set, increase the instance count or set to auto-scale on CPU usage. For either of these issues, contact the NVA vendor for assistance, as needed.

Validate VM Network statistics

If the VM network use spikes or shows periods of high usage, you may also have to increase the SKU size of the VM to obtain higher throughput capabilities. You can also redeploy the VM by having Accelerated Networking enabled. To verify whether the NVA supports Accelerated Networking feature, contact the NVA vendor for assistance, as needed.

Advanced network administrator troubleshooting

Capture network trace

Capture a simultaneous network trace on the source VM, the NVA, and the destination VM while you run PsPing or Nmap, and then stop the trace.

  1. To capture a simultaneous network trace, run the following command:

    For Windows

    netsh trace start capture=yes tracefile=c:\server_IP.etl scenario=netconnection

    For Linux

    sudo tcpdump -s0 -i eth0 -X -w vmtrace.cap

  2. Use PsPing or Nmap from the source VM to the destination VM (for example: PsPing or Nmap -p 80

  3. Open the network trace from the destination VM by using Network Monitor or tcpdump. Apply a display filter for the IP of the Source VM you ran PsPing or Nmap from, such as IPv4.address== (Windows netmon) or tcpdump -nn -r vmtrace.cap src or dst host (Linux).

Analyze traces

If you do not see the packets incoming to the backend VM trace, there is likely an NSG or UDR interfering or the NVA routing tables are incorrect.

If you do see the packets coming in but no response, then you may need to address a VM application or a firewall issue. For either of these issues, contact the NVA vendor for assistance as needed.