DHCP relay

DHCP Relay provides a way for DHCP clients to communicate with DHCP servers that are not available on the same local subnet/broadcast domain. When you enable DHCP Relay, Magic WAN Connector forwards DHCP discover messages to a predefined DHCP server, and routes the responses back to the original device that sent the discover message.

flowchart LR
accTitle: An example of Connector in DHCP Relay mode
    a(Magic WAN Connector) <--> b(Cloudflare/Magic WAN) <--> c(DHCP server)

    subgraph Site A
    d[LAN 1] <--> a
    e[LAN 2] <--> a
    end

    subgraph Site B
    c
    end
    classDef orange fill:#f48120,color: black
    class a,b,c orange

The above graph shows Connector sending DHCP discover messages to a DHCP server offsite.

Warning

DHCP relay will not work if your DHCP server is behind a Cloudflare Tunnel. To enable DHCP relay functionality, use either a Magic WAN tunnel or a CNI connection.

To configure DHCP relay:

Dashboard

1. Log in to the Cloudflare dashboard ↗ and select your account.
2. Go to Magic WAN > Connector on-ramps (beta).
3. Select your Connector > Edit.
4. Select Network Configuration.
5. In LAN configuration, select the LAN where you need to configure DHCP relay.
6. Select Edit.
7. Select This is a DHCP Relay.
8. In Upstream DHCP server addresses, enter the IP address of your DHCP server.
9. (Optional) If you need to add more DHCP server addresses, select Add upstream DHCP server address as many times as needed, and enter the new values.

API

Note

You will need your account ID and API Key to use the API.

Create a PUT request to update the LAN where you want to enable DHCP relay:

Example:

Required API token permissions

At least one of the following token permissions is required:

• Magic WAN Write
• Magic Transit Write

Update Site LAN

curl "https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/magic/sites/$SITE_ID/lans/$LAN_ID" \
  --request PUT \
  --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
  --json '{
    "lan": {
        "static_addressing": {
            "dhcp_relay": {
                "server_addresses": [
                    "192.0.2.1"
                ]
            }
        }
    }
  }'