--- title: Manage Backend Mapping --- # Manage Backend Mapping The **Backend Mapping** tab lists the backend groups behind a load balancer and lets you add, edit, and remove them after creation. A backend group is the pool of servers (or an auto scaling group) that receives traffic, along with its routing policy and health check. The Backend Mapping tab is available whenever the load balancer is not Creating, Deploying, or Deleting. For how routing policies and health checks behave, see [Choose a Load Balancer](/docs/myaccount/load-balancer/getting-started/choose-load-balancer#routing-policy). --- ## What the Tab Shows The columns differ by load balancer type. **Application Load Balancer (ALB):** Backend Group, Backend Type, Routing Policy, Protocol, Health Check, Servers, Socket Timeout, and Actions. **Network Load Balancer (NLB):** Backend Group, Routing Policy, LB Listening Port, Servers, and Actions. Each server appears as a chip showing its name, IP, and port. A server that is **DOWN** is shown in red. Health is read from the load balancer's monitoring data. --- ## Add, Edit, and Save 1. For an ALB, select **Add Backend Group** to create a new group, or the edit (pencil) icon on a row to change one. For an NLB, edit the existing backend. 2. Configure the group in the form (see below). 3. You can add or edit multiple groups before saving. When there are unsaved changes, a **Save and Deploy** button appears with an info icon next to changed rows. 4. Select **Save and Deploy** to apply. The load balancer redeploys with the new configuration (about 5–10 minutes). :::note You cannot delete the last backend group on its own. To remove the final backend, delete the entire load balancer instead. Editing and deleting are disabled while the load balancer is Powered off. ::: --- ## Backend Group Form (ALB) | Field | Type | Details | | ------------------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Backend Group | Text | Required, unique. Letters, digits, hyphen, underscore; up to 64 characters. | | Backend Protocol | Select | **HTTP** (default) or **HTTPS** — how the load balancer talks to the backends. HTTPS enables TLS to the backend (self-signed or internal-CA certificates are allowed). | | Health Check | Checkbox | Enables HTTP health checks. When on, a backend that returns a `2xx` or `3xx` response on the health-check path is marked **UP**; otherwise **DOWN**. The default path is `/`. | | Routing Policy | Select | **Source IP Hash** (default), **Round Robin**, or **Least Connection**. | | Backend Type | Select | **Node** (default) or **Auto Scale Group**. | | Backend Servers | Multi-select | Shown for **Node**. Select registered servers; use **Add Server** to add one (see below). | | Auto Scaling Group | Select | Shown for **Auto Scale Group**. Choose an [auto scaling group](/docs/myaccount/auto_scaling); use **Add New** to create one. | | Scaler Port | Number | Shown for **Auto Scale Group**. The port used to send and receive traffic (1–65535). | | Web Socket Timeout | Number | Optional. 1–100 seconds. | ### Add Server The **Add Server** modal registers a backend server: | Field | Requirement | | ----------- | ------------------------------------------------------------------------------------- | | Server Name | Required. Letters, digits, hyphen, underscore; up to 64 characters. | | Server IP | Required. A valid IPv4 address — prefer the private IP if the server is on E2E Cloud. | | Server Port | Required. 1–65535. | After you add servers, open the dropdown to review the list for the group. --- ## Backend Group Form (NLB) A Network Load Balancer forwards TCP traffic, so its form is simpler — there is no protocol, health-check checkbox, backend type, or WebSocket timeout. | Field | Type | Details | | ----------------- | ------------ | ------------------------------------------------------------------------------------------------------------------------ | | Backend Name | Text | Required. Letters, digits, hyphen, underscore; up to 64 characters. | | Routing Policy | Select | **Source IP Hash**, **Round Robin**, or **Least Connection** (Least Connection suits TCP). | | LB Listening Port | Number | Required. Must be **80**, **443**, or **1024–65535**. Ports **8080**, **10050**, and **9101** are reserved and rejected. | | Backends | Multi-select | Required. Add servers with **Add Server** (same fields as above). | :::note A Network Load Balancer supports a single TCP backend, and ACL rules cannot be applied to it. For content-based routing across multiple backend groups, use an [Application Load Balancer](/docs/myaccount/load-balancer/getting-started/create-application-load-balancer). ::: --- ## Rules and Limits - Backend group names must be unique on the load balancer, and `none` is not allowed as a name. - At least one backend group is required. - An NLB allows only one TCP backend; TCP and HTTP backends cannot be mixed. - ACL rules apply to ALBs only. --- ## Related Resources | Resource | Use it for | | ----------------------------------------------------------------------------------------------------------- | ------------------------------------------------- | | [ACL routing rules](/docs/myaccount/load-balancer/manage/acl) | Route requests to different backend groups (ALB). | | [Choose a Load Balancer](/docs/myaccount/load-balancer/getting-started/choose-load-balancer#routing-policy) | Routing policies and health checks explained. | | [Auto Scaling](/docs/myaccount/auto_scaling) | Use a dynamic scale group as a backend. | | [Troubleshoot Load Balancers](/docs/myaccount/load-balancer/troubleshoot) | Fix backends marked DOWN. |