Laird WB45NBT
Reference Guide
Embedded Wireless Solutions Support Center:
http://ews-support.lairdtech.com
www.lairdtech.com/wi-fi
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ones available; more complex configurations are also possible. Please contact Laird support if you have a use case this is
not covered in this document.
Choosing an Interface to the WB
The first consideration in configuring the Wi-Fi connectivity is what interface will be used between the host device and the
WB. The most common three options are Ethernet, USB Ethernet, and Serial (RS232). Each of these cases has the host
device sending and receiving IP packets and the WB forwarding packets to and from the Wi-Fi interface once connected.
Ethernet – Refers to the standard 802.3 Ethernet.
USB connectivity – We recommend setting up the WB to enable USB CDC Ethernet (also known as USB
Gadget Ethernet). Then installing the proper drivers on the host device. This allows the WB to appear as a
standard Ethernet network device.
Serial (RS232) – We recommend setting up PPP over serial on the WB and the host device and enabling IP
over PPP. Optionally, the host device can send raw byte data to a UART on the WB and the WB can
forward that data bi-directionally to a TCP socket via the built in socat program.
Configuring the WB to Use Layer 2 Bridging or Layer 3 NAT
The second consideration in configuring Wi-Fi connectivity is whether to configure the WB to act as a Layer 2 Bridge or a
Layer NAT device.
Layer 2 Bridge
When configured as a Layer 2 bridge, the WB acts as a transparent bridge for Layer 2 packets carrying an IP-based packet
from the host device. The WB expects the host to do all Layer 3 IP configuration such as static addressing or DHCP for the
Wi-Fi network. This mode applies to Ethernet to Wi-Fi and USB Ethernet to Wi-Fi. In the Layer 2 Bridge configuration, it
appears to the host device that it is connected to a physical network.
Layer 3 NAT
When configured to do Layer 3 NAT, the WB is configured to run a DHCP client or have a static IP address on the WB’s Wi-
Fi interface. In this configuration, a static non-routable IP address is assigned on the host device’s communication
interface and the corresponding interface on the WB. Port NAT and IP masquerading would then enable seamless
communication from the host interface to the Wi-Fi network. This mode applies to Ethernet to Wi-Fi, USB Ethernet to Wi-
Fi, and Serial PPP to Wi-Fi. Seven common use cases are detailed that describe the WB configured as a bridge or NAT
device.
Note: Please contact Laird support if you have a use case not covered here in this document.
Choosing Layer 2 Bridge or Layer 3 NAT – Use Cases
Use Case 1
A single host device with a DHCP client for Wi-Fi on the host device’s Ethernet or USB interface to the WB.
This is often used when the WB if functioning as an Ethernet to Wi-Fi dongle on an existing product where the Ethernet is
set up to use DHCP.
Solution: Bridging
The WB acts as a transparent bridge between the Ethernet or USB and Wi-Fi.
Caveats:
It should send a ping packet or other IP packet from the host device’s interface to the WB once a new IP
address has been assigned to register the host device with the WB’s bridge code. Otherwise, the bridge
may not forward incoming Wi-Fi packets to the host device.
