> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xloud.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Create and Manage Subnets

> Add, configure, and manage subnets within Xloud tenant networks. Control DHCP, allocation pools, DNS, and host routes from the Dashboard or CLI.

## Overview

Subnets define the IP address space within a network. Each subnet specifies a CIDR block,
optional DHCP assignment, a gateway IP, and DNS resolvers that are pushed to instances at
boot. A single network can host multiple subnets — e.g., one IPv4 and one IPv6
range — or separate subnets for different application tiers.

<Note>
  **Prerequisites**

  * An existing Xloud tenant network (see [Create a Network](/services/networking/create-network))
  * Dashboard access or CLI configured with valid credentials
</Note>

***

## Add a Subnet to an Existing Network

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    <Steps titleSize="h3">
      <Step title="Open the network" icon="compass">
        Navigate to **Network > Networks** and click the network name to open it.
      </Step>

      <Step title="Add a subnet" icon="plus">
        Click the **Subnets** tab, then click **Create Subnet**.
      </Step>

      <Step title="Configure CIDR and gateway" icon="settings">
        | Field           | Description                                                          |
        | --------------- | -------------------------------------------------------------------- |
        | **Subnet Name** | Descriptive name, e.g., `db-subnet`                                  |
        | **CIDR**        | CIDR block, e.g., `10.0.2.0/24`                                      |
        | **IP Version**  | IPv4 or IPv6                                                         |
        | **Gateway IP**  | Optional — leave blank for auto-assign or enter `0.0.0.0` to disable |
      </Step>

      <Step title="Configure DHCP and allocation options" icon="sliders">
        | Option               | Description                                                     |
        | -------------------- | --------------------------------------------------------------- |
        | **Enable DHCP**      | Provide automatic IP assignment for instances on this subnet    |
        | **Allocation Pools** | Restrict the DHCP-assigned range, e.g., `10.0.2.10,10.0.2.200`  |
        | **DNS**              | Comma-separated list of resolvers                               |
        | **Host Routes**      | Static routes injected via DHCP in `destination,nexthop` format |

        <Tip>
          Use allocation pools to reserve address ranges for manually configured hosts
          such as database nodes or network appliances with static IPs.
        </Tip>
      </Step>

      <Step title="Create the subnet" icon="circle-check">
        Click **Create** to save the subnet.

        <Check>The subnet appears in the network's Subnets tab with status **Active**.</Check>
      </Step>
    </Steps>
  </Tab>

  <Tab title="CLI" icon="terminal">
    <Steps titleSize="h3">
      <Step title="Authenticate" icon="key">
        Source your credentials file to authenticate with the Xloud platform:

        ```bash title="Load credentials" theme={null}
        source openrc.sh
        ```

        <Tip>
          Your administrator provides the RC (credentials) file for your project. See [CLI Setup](/cli-setup) for configuration details.
        </Tip>
      </Step>

      <Step title="Add subnet with DHCP" icon="plus">
        ```bash title="Create subnet with allocation pool" theme={null}
        openstack subnet create db-subnet \
          --network app-network \
          --subnet-range 10.0.2.0/24 \
          --gateway 10.0.2.1 \
          --allocation-pool start=10.0.2.10,end=10.0.2.200 \
          --dns-nameserver 8.8.8.8
        ```
      </Step>

      <Step title="Add subnet without DHCP (static IPs)" icon="minus">
        ```bash title="Create subnet with DHCP disabled" theme={null}
        openstack subnet create db-subnet-static \
          --network app-network \
          --subnet-range 10.0.2.0/24 \
          --no-dhcp
        ```

        Use `--no-dhcp` for subnets where IP assignments are managed manually — e.g.,
        database tiers where each node is pre-configured with a fixed address.
      </Step>

      <Step title="Verify" icon="circle-check">
        ```bash title="Show subnet details" theme={null}
        openstack subnet show db-subnet
        ```

        <Check>Confirm the CIDR, gateway, and DHCP settings match the intended configuration.</Check>
      </Step>
    </Steps>
  </Tab>
</Tabs>

***

## Subnet Management Operations

### Update DNS Resolvers

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    Navigate to **Network > Networks**, open the subnet row, and click **Edit Subnet**.
    Update the **DNS** field in the **Advanced Options**.
  </Tab>

  <Tab title="CLI" icon="terminal">
    ```bash title="Update DNS on a subnet" theme={null}
    openstack subnet set app-subnet \
      --dns-nameserver 10.0.0.53 \
      --dns-nameserver 8.8.8.8
    ```

    Existing instances pick up the new resolvers on their next DHCP renewal. To apply
    immediately inside the guest OS, run `dhclient -r && dhclient` on the instance.
  </Tab>
</Tabs>

### Add Host Routes

Host routes are injected via DHCP and add static routing entries on the guest OS. Use
them to direct traffic for specific CIDRs through a dedicated gateway.

```bash title="Add host route to subnet" theme={null}
openstack subnet set app-subnet \
  --host-route destination=172.16.0.0/12,gateway=192.168.10.254
```

### Disable or Enable DHCP

```bash title="Disable DHCP on a subnet" theme={null}
openstack subnet set app-subnet --no-dhcp
```

```bash title="Re-enable DHCP on a subnet" theme={null}
openstack subnet set app-subnet --dhcp
```

<Warning>
  Disabling DHCP on a subnet that has instances running will cause those instances to
  fail IP renewal on the next lease expiry. Ensure all instances on the subnet are
  configured with static IPs before disabling DHCP.
</Warning>

***

## Subnet Configuration Reference

| Parameter       | CLI Flag               | Description                                         |
| --------------- | ---------------------- | --------------------------------------------------- |
| CIDR            | `--subnet-range`       | IP address range in CIDR notation                   |
| Gateway         | `--gateway`            | Default gateway IP for DHCP clients                 |
| DHCP            | `--dhcp` / `--no-dhcp` | Enable or disable automatic IP assignment           |
| Allocation Pool | `--allocation-pool`    | Start/end range for DHCP-assigned addresses         |
| DNS Servers     | `--dns-nameserver`     | Resolvers pushed to instances (repeat for multiple) |
| Host Routes     | `--host-route`         | Static routes injected via DHCP                     |
| IP Version      | `--ip-version`         | `4` for IPv4, `6` for IPv6                          |

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Routers and Gateways" href="/services/networking/routers" color="#197560">
    Attach subnets to a router to enable inter-subnet routing and internet access
  </Card>

  <Card title="DNS Configuration" href="/services/networking/dns-config" color="#197560">
    Configure DNS name servers and hostname resolution for your subnets
  </Card>

  <Card title="Create a Network" href="/services/networking/create-network" color="#197560">
    Create the network that hosts your subnets
  </Card>

  <Card title="Network Troubleshooting" href="/services/networking/troubleshooting" color="#197560">
    Diagnose and resolve subnet connectivity and DHCP issues
  </Card>
</CardGroup>