In C# how to get the VMSS instance private IP

hi Ankit,

Thank you very much for your prompt response. I have try using your code, however Microsoft.Azure.Management.Fluent seem is deprecated and not suggested to use. We are actually will use Azure Function and write the code in C#. We will use DefaultAzureCredential() credential for Azure Function to get the private IP of VMSS instance (we have assigned the permission).

Would you able to provide the solution by using latest SDK of Azure?
eg. Azure.ResourceManager, Azure.Identity

Hello pipi,

I've generated this code using internal tool, can you try below code if it helps to work for you.

using System;

using System.Linq;

using System.Threading.Tasks;

using Azure;

using Azure.Identity;

using Azure.ResourceManager;

using Azure.ResourceManager.Compute;

using Azure.ResourceManager.Network;

public class VmssNetworkingHelper

{

    /// <summary>

    /// Returns the private IP address of a VMSS instance.

    /// Prefers the primary NIC and primary IP configuration if present.

    /// </summary>

    public async Task<string> GetVmssInstancePrivateIpAsync(

        string subscriptionId,

        string resourceGroupName,

        string vmssName,

        string instanceId)

    {

        // DefaultAzureCredential works well in Azure Functions, supports Managed Identity & environment vars.

        var credential = new DefaultAzureCredential();

        var armClient = new ArmClient(credential, subscriptionId);

        try

        {

            // Resolve the VMSS resource

            var vmssId = VirtualMachineScaleSetResource.CreateResourceIdentifier(subscriptionId, resourceGroupName, vmssName);

            var vmss = armClient.GetVirtualMachineScaleSetResource(vmssId);

            // Get the specific VMSS VM resource (instance)

            var vmssVmResource = vmss.GetVirtualMachineScaleSetVmResource(instanceId);

            var vmssVmResponse = await vmssVmResource.GetAsync();

            var vmssVm = vmssVmResponse.Value;

            // Defensive checks

            if (vmssVm?.Data?.NetworkProfile?.NetworkInterfaces == null || vmssVm.Data.NetworkProfile.NetworkInterfaces.Count == 0)

                throw new InvalidOperationException("The VMSS VM has no network interfaces attached.");

            // Prefer the primary NIC if available; otherwise use the first one

            var nicRefs = vmssVm.Data.NetworkProfile.NetworkInterfaces;

            var primaryNicRef = nicRefs.FirstOrDefault(n => n.Primary == true) ?? nicRefs.First();

            if (string.IsNullOrWhiteSpace(primaryNicRef.Id))

                throw new InvalidOperationException("The NIC reference does not contain a valid resource ID.");

            // Parse the NIC resource ID to extract the NIC name

            var nicResourceId = new ResourceIdentifier(primaryNicRef.Id);

            var nicName = nicResourceId.Name;

            if (string.IsNullOrWhiteSpace(nicName))

                throw new InvalidOperationException("Unable to parse NIC name from NIC resource ID.");

            // Get the NIC resource

            var nicId = NetworkInterfaceResource.CreateResourceIdentifier(subscriptionId, resourceGroupName, nicName);

            var nicResource = armClient.GetNetworkInterfaceResource(nicId);

            var nicResponse = await nicResource.GetAsync();

            var nic = nicResponse.Value;

            if (nic?.Data?.IPConfigurations == null || nic.Data.IPConfigurations.Count == 0)

                throw new InvalidOperationException("The NIC has no IP configurations.");

            // Prefer the primary IP configuration; otherwise use the first with a private IP

            var primaryIpConfig = nic.Data.IPConfigurations.FirstOrDefault(ipc => ipc.Primary == true)

                                  ?? nic.Data.IPConfigurations.FirstOrDefault(ipc => !string.IsNullOrEmpty(ipc.PrivateIPAddress));

            if (primaryIpConfig == null)

                throw new InvalidOperationException("No IP configuration with a private IP address was found.");

            if (string.IsNullOrEmpty(primaryIpConfig.PrivateIPAddress))

            {

                // Fallback: search all IP configs for any private IP

                var anyPrivateIp = nic.Data.IPConfigurations

                    .Select(ipc => ipc.PrivateIPAddress)

                    .FirstOrDefault(ip => !string.IsNullOrEmpty(ip));

                if (string.IsNullOrEmpty(anyPrivateIp))

                    throw new InvalidOperationException("No private IP address found on any NIC IP configuration.");

                return anyPrivateIp;

            }

            return primaryIpConfig.PrivateIPAddress;

        }

        catch (Exception ex)

        {

            // Wrap with context; preserve the original exception for diagnostics

            throw new Exception(

                $"Error retrieving private IP for VMSS '{vmssName}', instance '{instanceId}' in RG '{resourceGroupName}': {ex.Message}",

                ex);

        }

    }

}