Virtual Network name must be valid

April 16, 2025 · View on GitHub

SYNOPSIS

Azure Resource Manager (ARM) has requirements for Virtual Network names.

DESCRIPTION

When naming Azure resources, resource names must meet service requirements. The requirements for Virtual Network names are:

Between 2 and 64 characters long.
Alphanumerics, underscores, periods, and hyphens.
Start with alphanumeric.
End alphanumeric or underscore.
VNET names must be unique within a resource group.

RECOMMENDATION

Consider using names that meet Virtual Network naming requirements. Additionally consider naming resources with a standard naming convention.

EXAMPLES

Configure with Bicep

To deploy virtual networks that pass this rule:

Set the name property to a string that matches the naming requirements.
Optionally, consider constraining name parameters with minLength and maxLength attributes.

For example:

@minLength(2)
@maxLength(64)
@description('The name of the resource.')
param name string

@description('The location resources will be deployed.')
param location string = resourceGroup().location

// An example virtual network (VNET) with NSG configured.
resource vnet 'Microsoft.Network/virtualNetworks@2024-05-01' = {
  name: name
  location: location
  properties: {
    addressSpace: {
      addressPrefixes: [
        '10.0.0.0/16'
      ]
    }
    dhcpOptions: {
      dnsServers: [
        '10.0.1.4'
        '10.0.1.5'
      ]
    }
    subnets: [
      {
        name: 'GatewaySubnet'
        properties: {
          addressPrefix: '10.0.0.0/24'
        }
      }
      {
        name: 'snet-001'
        properties: {
          addressPrefix: '10.0.1.0/24'
          networkSecurityGroup: {
            id: nsg.id
          }
        }
      }
      {
        name: 'snet-002'
        properties: {
          addressPrefix: '10.0.2.0/24'
          delegations: [
            {
              name: 'HSM'
              properties: {
                serviceName: 'Microsoft.HardwareSecurityModules/dedicatedHSMs'
              }
            }
          ]
        }
      }
    ]
  }
}

Configure with Azure template

To deploy virtual networks that pass this rule:

Set the name property to a string that matches the naming requirements.
Optionally, consider constraining name parameters with minLength and maxLength attributes.

For example:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "metadata": {
    "_generator": {
      "name": "bicep",
      "version": "0.34.44.8038",
      "templateHash": "4612577866627056405"
    }
  },
  "parameters": {
    "name": {
      "type": "string",
      "minLength": 2,
      "maxLength": 64,
      "metadata": {
        "description": "The name of the resource."
      }
    },
    "location": {
      "type": "string",
      "defaultValue": "[resourceGroup().location]",
      "metadata": {
        "description": "The location resources will be deployed."
      }
    }
  },
  "resources": [
    {
      "type": "Microsoft.Network/virtualNetworks",
      "apiVersion": "2024-05-01",
      "name": "[parameters('name')]",
      "location": "[parameters('location')]",
      "properties": {
        "addressSpace": {
          "addressPrefixes": [
            "10.0.0.0/16"
          ]
        },
        "dhcpOptions": {
          "dnsServers": [
            "10.0.1.4",
            "10.0.1.5"
          ]
        },
        "subnets": [
          {
            "name": "GatewaySubnet",
            "properties": {
              "addressPrefix": "10.0.0.0/24"
            }
          },
          {
            "name": "snet-001",
            "properties": {
              "addressPrefix": "10.0.1.0/24",
              "networkSecurityGroup": {
                "id": "[resourceId('Microsoft.Network/networkSecurityGroups', parameters('name'))]"
              }
            }
          },
          {
            "name": "snet-002",
            "properties": {
              "addressPrefix": "10.0.2.0/24",
              "delegations": [
                {
                  "name": "HSM",
                  "properties": {
                    "serviceName": "Microsoft.HardwareSecurityModules/dedicatedHSMs"
                  }
                }
              ]
            }
          }
        ]
      },
      "dependsOn": [
        "[resourceId('Microsoft.Network/networkSecurityGroups', parameters('name'))]"
      ]
    }
  ]
}

NOTES

This rule does not check if Virtual Network names are unique.