# Security

You can allow or deny user access to a gateway based on a MAC address. This can be accomplished using the **Security** tab in the **RAS Secure Gateway Properties** dialog.

To use Site default settings, click the **Inherit default settings** option. To specify your own settings, clear the option.

To configure a list of allowed or denied MAC addresses, click the **Security** tab and select one of the following options:

* **Allow all except.** All devices on the network will be allowed to connect to the gateway except those included in this list. Click **Tasks** > **Add** to select a device or to specify a MAC address.
* **Allow only**. Only the devices with the MAC addresses included in the list are allowed to connect to the gateway. Click **Tasks** > **Add** to select a device or to specify a MAC address.

Please note that the Gateway MAC address filtering is based on ARP, so client and server must be on the same network for the filtering to work. It does not work across network boundaries.