グローバル サブネットは、グローバル API サーバー内に作成されたサブネットです。これらのサブネットは、グローバル外部ロードバランサ（ELB）と内部ロードバランサ（ILB）に必要です。グローバル サブネットを使用すると、複数の GDC ゾーンにまたがるグローバル インフラストラクチャのさまざまな部分からアクセス可能な IP アドレスを割り当てることができます。
グローバル サブネットを使用して、次のタスクを行います。
ILB IP アドレスの親 CIDR を指定する:Branch タイプのグローバル親サブネットを作成して、内部ロードバランサ専用の IP アドレス プールを管理できます。
[[["わかりやすい","easyToUnderstand","thumb-up"],["問題の解決に役立った","solvedMyProblem","thumb-up"],["その他","otherUp","thumb-up"]],[["わかりにくい","hardToUnderstand","thumb-down"],["情報またはサンプルコードが不正確","incorrectInformationOrSampleCode","thumb-down"],["必要な情報 / サンプルがない","missingTheInformationSamplesINeed","thumb-down"],["翻訳に関する問題","translationIssue","thumb-down"],["その他","otherDown","thumb-down"]],["最終更新日 2025-09-04 UTC。"],[],[],null,["# About subnets for load balancing\n\nThis page provides an overview of subnets in Google Distributed Cloud (GDC) air-gapped and\ntheir role in your load balancing efforts. A subnet, or subnetwork, represents a\nlogical subdivision of an IP network. This segmentation enhances network\nefficiency, security, and manageability. For more information on subnets, see\n[Subnets and IP addresses in\nGDC](/distributed-cloud/hosted/docs/latest/gdch/platform/pa-user/subnets-overview).\n\nThis page is for developers within the application operator group who want to\nestablish a secure air-gapped connection and balance workloads across zones. For\nmore information, see [Audiences for GDC air-gapped\ndocumentation](/distributed-cloud/hosted/docs/latest/gdch/resources/audiences).\n\nGlobal subnets for load balancing\n---------------------------------\n\nA *global subnet* is a subnet created within the global API server. These\nsubnets are required for global external load balancers (ELB) and internal load\nbalancers (ILB). Global subnets enable the allocation of IP addresses that are\naccessible across different parts of a global infrastructure, spanning multiple\nGDC zones.\n\nYou use global subnets to complete the following tasks:\n\n- **Provide parent CIDRs for ILB IP addresses:** A global parent subnet of type `Branch` can be created to manage a pool of IP addresses specifically for internal load balancers.\n- **Allocate single IP addresses for ILB and ELB services:** Global leaf subnets are used to reserve a single Virtual IP (VIP) address for a specific ILB or ELB.\n- **Enable anycast IPs for ELBs:** For ELBs, a specific global parent subnet is used to allocate anycast IP addresses, which are essential for global external accessibility.\n\nSubnets and forwarding rules\n----------------------------\n\nThe direct link between a global subnet and a load balancer's functionality is\nestablished through the forwarding rule resource. A forwarding rule references a\nglobal leaf subnet to obtain the VIP address that clients use to\naccess the load balancing service.\n\nHere's an example showing how the configuration works:\n\n1. A global leaf subnet is created with a `prefixLength` value of `32`, indicating that the subnet allocates a single IP address.\n2. This allocated IP address, identified by the name of the leaf subnet, is then specified in the `cidrRef` field of either a `ForwardingRuleInternal` resource for ILBs or `ForwardingRuleExternal` resource for ELBs.\n3. This link makes the load balancer's forwarding rule use a dedicated and globally managed IP address provided by the subnet.\n\nWhat's next\n-----------\n\n- [Create a global subnet for internal load balancing](/distributed-cloud/hosted/docs/latest/gdch/platform/pa-user/create-global-subnet-ilb)\n- [Create a global subnet for external load balancing](/distributed-cloud/hosted/docs/latest/gdch/platform/pa-user/create-global-subnet-elb)"]]
