★★ 中級

03. VNet とネットワーク

Azure の仮想ネットワーク。AWS の VPC に相当しますが、NSG（Network Security Group）の動き方や Subnet と NSG の関連付け方など、Azure 固有の作法があります。

この章の目次

AWS との対応表

AzureAWS備考
Virtual Network (VNet)VPCregion 単位
SubnetSubnetAzure は AZ を意識しないことが多い（Zone は VM 側で指定）
Network Security Group (NSG)Security Group + NACLNSG は Subnet にも NIC にも付けられる
Route TableRoute Table明示しなければ system route
NAT GatewayNAT Gateway用途同じ
Public IPEIP静的 / 動的の選択

azurerm_virtual_network

resource "azurerm_virtual_network" "main" {
  name                = "vnet-myapp-prd-jpe"
  resource_group_name = azurerm_resource_group.main.name
  location            = azurerm_resource_group.main.location
  address_space       = ["10.0.0.0/16"]

  tags = local.common_tags
}

azurerm_subnet

resource "azurerm_subnet" "public" {
  name                 = "snet-public"
  resource_group_name  = azurerm_resource_group.main.name
  virtual_network_name = azurerm_virtual_network.main.name
  address_prefixes     = ["10.0.1.0/24"]
}

resource "azurerm_subnet" "private" {
  name                 = "snet-private"
  resource_group_name  = azurerm_resource_group.main.name
  virtual_network_name = azurerm_virtual_network.main.name
  address_prefixes     = ["10.0.11.0/24"]

  # サブネットレベルの委任（Container Apps、Functions Premium 等で必要）
  delegation {
    name = "Microsoft.App.environments"
    service_delegation {
      name = "Microsoft.App/environments"
    }
  }
}

NSG とルール

AWS の Security Group との大きな違い: NSG は Allow / Deny の両方を書ける。priority の数字が小さいほど優先。

resource "azurerm_network_security_group" "web" {
  name                = "nsg-web-prd"
  resource_group_name = azurerm_resource_group.main.name
  location            = azurerm_resource_group.main.location

  security_rule {
    name                       = "AllowHTTPS"
    priority                   = 100
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "*"
    destination_port_range     = "443"
    source_address_prefix      = "Internet"        # サービスタグ
    destination_address_prefix = "*"
  }

  security_rule {
    name                       = "AllowSSHFromBastion"
    priority                   = 110
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "*"
    destination_port_range     = "22"
    source_address_prefix      = "10.0.99.0/24"    # 踏み台サブネット
    destination_address_prefix = "*"
  }

  security_rule {
    name                       = "DenyAllInbound"
    priority                   = 4096               # 最低優先（最後に評価）
    direction                  = "Inbound"
    access                     = "Deny"
    protocol                   = "*"
    source_port_range          = "*"
    destination_port_range     = "*"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  }
}
サービスタグ Internet / VirtualNetwork / AzureLoadBalancer など、Azure 側が管理する IP セットを名前で参照できる。CIDR を直書きするより便利で安全。

Subnet と NSG の関連付け

これを書かないと NSG が 「作っただけで適用されていない」 状態になる。

resource "azurerm_subnet_network_security_group_association" "public" {
  subnet_id                 = azurerm_subnet.public.id
  network_security_group_id = azurerm_network_security_group.web.id
}

NAT Gateway

resource "azurerm_public_ip" "nat" {
  name                = "pip-nat-prd"
  resource_group_name = azurerm_resource_group.main.name
  location            = azurerm_resource_group.main.location
  allocation_method   = "Static"
  sku                 = "Standard"
}

resource "azurerm_nat_gateway" "main" {
  name                = "natgw-prd"
  resource_group_name = azurerm_resource_group.main.name
  location            = azurerm_resource_group.main.location
  sku_name            = "Standard"
}

resource "azurerm_nat_gateway_public_ip_association" "main" {
  nat_gateway_id       = azurerm_nat_gateway.main.id
  public_ip_address_id = azurerm_public_ip.nat.id
}

resource "azurerm_subnet_nat_gateway_association" "private" {
  subnet_id      = azurerm_subnet.private.id
  nat_gateway_id = azurerm_nat_gateway.main.id
}

完成形

上記要素を組み合わせれば、AWS 章 02 と同等の Web 3 層基盤が VNet 上に構築できます。実装は modules/network/ としてモジュール化するのが定石。

← 前へ02. Resource Group