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Fix Azure Virtual Network Nsg Errors

DodaTech Updated 2026-06-26 2 min read

When working with Azure Virtual Network, you may encounter a configuration error that prevents your deployment from working. This guide explains the most common mistake with nsg and shows the exact fix.

A Common Mistake

Creating a Network Security Group (NSG) with overly permissive rules (e.g., allowing all traffic from any source), creating a security vulnerability.

The incorrect command:

az network nsg create --name my-nsg --resource-group my-rg
az network nsg rule create --name allow-all --nsg-name my-nsg --resource-group my-rg --priority 100 --direction Inbound --access Allow --protocol * --source-address-prefixes * --source-port-ranges * --destination-address-prefixes * --destination-port-ranges *

Error output:

NSG rule created: Allow all inbound traffic from any source.
This is equivalent to disabling the firewall. Any internet host can reach any port on any VM in the subnet. Attackers can scan for open ports, exploit vulnerabilities, and gain access.

The Correct Approach

The right way to configure nsg in Azure Virtual Network:

az network nsg create --name my-nsg --resource-group my-rg
az network nsg rule create --name allow-ssh --nsg-name my-nsg --resource-group my-rg --priority 100 --direction Inbound --access Allow --protocol Tcp --source-address-prefixes 203.0.113.0/24 --source-port-ranges * --destination-address-prefixes 10.100.1.0/24 --destination-port-ranges 22
az network nsg rule create --name deny-all --nsg-name my-nsg --resource-group my-rg --priority 1000 --direction Inbound --access Deny --protocol * --source-address-prefixes * --source-port-ranges * --destination-address-prefixes * --destination-port-ranges *

Successful result:

NSG rules created.
Only SSH from the management IP range is allowed. All other inbound traffic is denied. Default NSG rules (AllowVNetInBound, AllowAzureLoadBalancerInBound, DenyAllInBound) are overridden appropriately.

How to Prevent This

Follow Least Privilege: allow only required ports and source IPs. Use application security groups (ASGs) for rule organization. NSG flow logs capture traffic for analysis. Default rules cannot be deleted but can be overridden with higher priority denies. NSGs can be applied to subnets or NICs.

FAQ

Why does my nsg configuration fail in Azure Virtual Network?

Configuration failures in Azure often stem from missing role assignments, incorrect resource IDs, region availability issues, or ARM template parameter errors. Always use az --help to verify command syntax and parameter names. Check Azure Activity Log for detailed error traces.

How do I debug nsg issues in Azure?

Use az monitor activity-log list to audit operations. For resource issues, use az resource show. For networking, use Network Watcher diagnostics. For role issues, check az role assignment list. Enable diagnostic settings for detailed logging. Use az rest to call Azure REST APIs directly for debugging.

What are the best practices for nsg in Azure?

Use infrastructure-as-code (ARM, Terraform, Bicep) for all configurations. Tag resources for cost tracking and management. Use Azure Policy for governance. Enable diagnostic logs and monitoring. Follow Least Privilege for RBAC. Test in a non-production environment first. Review Azure Advisor recommendations regularly.

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