The AirPort Base Station may be set up to act as only a bridge to your Ethernet network. To do so, follow these steps:
1. Open the AirPort Admin Utility.
2. Click the Network tab.
3. Ensure the checkbox for Distribute IP addresses is unchecked, as shown in Figure 1.
This turns off Network Address Translation (NAT) and DHCP routing in the base station making it act as a bridge only.
Note: With NAT and DHCP disabled, the AirPort Setup Assistant will not be able to communicate with the Base Station.
Figure 1 AirPort Admin Utility window
Note: When you use an AirPort-equipped computer as an AirPort Software Base Station, the bridging feature is not available.
Note: Wireless Internet access requires an Internet service provider (fees may apply) and AirPort (or AirPort-compatible) wireless Ethernet card and base station. Some ISPs are not compatible with AirPort. For more information, see technical document 106590: "
AirPort: Requirements for Wireless Internet Access"