# MAC (B3)

To set the CG1018 to operate with B3 server define **URL\_MAC=1**. 

**If URL\_MAC=1**, the settings for B2 and Coolguard (RQS) had no influence.

The settings shown below set **MAC** (B3) mode and define server as **boomerang3.com**.

{% code overflow="wrap" %}

```sh
# B3:
#URL_MAC=0 -> Uses the SERVICE_URL to get status from server (older behaviour of Blixtljus)
#URL_MAC=1 -> Default behaviour, uses the URL_MAC_BASE + the MAC-adress to generate a unique URL only used by this unit, for example: http://www.boomerang3.com/bl/MAC/?id=B827EB29CA0D
URL_MAC=1
URL_MAC_BASE="https://boomerang3.com/api/relaybox"
```

{% endcode %}

In this mode the URL consists of two parts, where the first is defined at URL\_MAC\_BASE and is the same for all CG1018 that communicates with the same server.

For the server to distinguish between different Relay Boxes, the MAC address of the specific unit is automatically appended to the URL in the GET request sent to the server, so it looks as shown in the example below:

If

```sh
URL_MAC_BASE:"http://boomerang3.com/api/RelayBox"
CG1018 MAC address: B8:27:EB:29:CA:0D
```

then the automatically generated URL is:

```sh
http://boomerang3.com/api/RelayBox/?id=B827EB29CA0D
```

{% hint style="info" %}
Note that you **only need** to fill in the URL\_MAC\_BASE of the B3 server, the MAC address is added automatically.
{% endhint %}

The details of packets exchange in B3 mode can be found in [Wireshark logs](/cg1018-relay-box-installation-manual/troubleshooting/wireshark-logs.md).


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