> ## 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.

# DNS Configuration

> Configure DNS name servers and hostname resolution for Xloud tenant subnets. Push resolvers to instances via DHCP for private and public name resolution.

## Overview

DNS configuration in Xloud Networking controls which resolvers instances use for hostname
resolution. Name servers are set at the subnet level and pushed to instances via DHCP at
boot time. You can configure private internal resolvers, public fallback resolvers, or a
combination — giving instances access to both internal service hostnames and public domain
names.

<Note>
  **Prerequisites**

  * An existing subnet with DHCP enabled ([Create and Manage Subnets](/services/networking/subnets))
  * Dashboard access or CLI configured with valid credentials
</Note>

***

## Configure DNS on a Subnet

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    <Steps titleSize="h3">
      <Step title="Open the subnet for editing" icon="compass">
        Navigate to
        **Network > Networks**. Click the network name, open the **Subnets** tab,
        and click **Edit Subnet** on the target subnet.
      </Step>

      <Step title="Update DNS">
        In the **Advanced Options** section, update the **DNS** field.
        Enter one resolver per line.

        | Resolver Type     | Example     | Use Case                                        |
        | ----------------- | ----------- | ----------------------------------------------- |
        | Internal resolver | `10.0.0.53` | Resolve private hostnames (e.g., `db.internal`) |
        | Public fallback   | `8.8.8.8`   | Resolve public internet domains                 |
        | Secondary public  | `8.8.4.4`   | Redundant public resolver                       |

        <Tip>
          Place your internal resolver first. Instances try resolvers in the order they
          are listed — putting the internal resolver first speeds up private hostname lookups.
        </Tip>
      </Step>

      <Step title="Save and verify" icon="circle-check">
        Click **Save**. Existing instances pick up the new resolvers on their next DHCP renewal.

        <Check>New instances launched on this subnet receive the updated DNS resolvers automatically.</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="Set DNS resolvers on a subnet" icon="settings">
        ```bash title="Update DNS name servers" theme={null}
        openstack subnet set app-subnet \
          --dns-nameserver 10.0.0.53 \
          --dns-nameserver 8.8.8.8
        ```

        Repeat `--dns-nameserver` for each resolver. The order of the flags determines
        the resolver priority.
      </Step>

      <Step title="Verify the configuration" icon="circle-check">
        ```bash title="Show subnet DNS config" theme={null}
        openstack subnet show app-subnet -f json | grep dns_nameservers
        ```

        <Check>Output lists the configured resolvers in priority order.</Check>
      </Step>
    </Steps>
  </Tab>
</Tabs>

***

## Apply DNS Changes to Running Instances

DNS resolvers are delivered via DHCP at instance boot. Running instances retain their
current resolvers until their DHCP lease renews or you force a renewal.

<Tabs>
  <Tab title="Linux instances" icon="terminal">
    ```bash title="Force DHCP renewal (systemd-networkd)" theme={null}
    sudo networkctl renew eth0
    ```

    ```bash title="Force DHCP renewal (NetworkManager)" theme={null}
    sudo nmcli device reapply eth0
    ```

    ```bash title="Force DHCP renewal (dhclient)" theme={null}
    sudo dhclient -r eth0 && sudo dhclient eth0
    ```
  </Tab>

  <Tab title="Verify resolution" icon="circle-check">
    After renewal, confirm the instance is using the updated resolvers:

    ```bash title="Check /etc/resolv.conf" theme={null}
    cat /etc/resolv.conf
    ```

    ```bash title="Test internal resolution" theme={null}
    nslookup db.internal 10.0.0.53
    ```

    ```bash title="Test public resolution" theme={null}
    nslookup google.com 8.8.8.8
    ```

    <Check>Both internal and public hostnames resolve correctly.</Check>
  </Tab>
</Tabs>

***

## Remove DNS Resolvers

```bash title="Clear DNS name servers from subnet" theme={null}
openstack subnet set app-subnet --no-dns-nameservers
```

<Warning>
  Removing all DNS resolvers means instances will have no resolvers after their next
  DHCP renewal. They will be unable to resolve any hostnames, including internal ones.
  Always configure at least one resolver.
</Warning>

***

## DNS Reference

| Resolver           | Address              | Notes                                          |
| ------------------ | -------------------- | ---------------------------------------------- |
| Google Public DNS  | `8.8.8.8`, `8.8.4.4` | Low-latency, widely available                  |
| Cloudflare DNS     | `1.1.1.1`, `1.0.0.1` | Privacy-focused, fast                          |
| Internal (example) | `10.0.0.53`          | Resolves private hostnames within your cluster |

<Info>
  For deployments with a dedicated DNS service, Xloud Networking supports the optional
  DNS service (Xloud DNS) which provides zone management, record lifecycle, and floating
  IP-to-hostname associations. Contact your administrator to enable Xloud DNS.
</Info>

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Create and Manage Subnets" href="/services/networking/subnets" color="#197560">
    Manage all subnet settings including DHCP, allocation pools, and host routes
  </Card>

  <Card title="Network Troubleshooting" href="/services/networking/troubleshooting" color="#197560">
    Diagnose DHCP and name resolution failures on your instances
  </Card>

  <Card title="Floating IP Addresses" href="/services/networking/floating-ips" color="#197560">
    Assign public IPs to instances with DNS-resolvable hostnames
  </Card>

  <Card title="Network Topologies" href="/services/networking/network-topology" color="#197560">
    Design multi-tier topologies with DNS-aware subnets
  </Card>
</CardGroup>