AirPort Admin Utility 1.2: Network Tab Explained
Figure 1 AirPort Admin Utility 1.2 Network Tab
Distribute IP addresses
When you select "Distribute IP addresses", options such as DHCP (Dynamic Host Configuration Protocol) and NAT (Network Address Translation) are available. These options are explained in this article.
When this checkbox is unselected, the base station acts as a bridge. This makes the base station pass network traffic from the wireless network to the wired network without manipulation. When you configure the base station to join your two networks in this way, your wireless client computers must each have TCP/IP (Transmission Control Protocol/Internet Protocol) configurations that are valid for the wired network.
Note: You can set up bridging as a troubleshooting step if you think that your Internet Service Provider's (ISP) network does not work with some feature of the base station.
For more information on bridging see article 58597: "AirPort Base Station: Configuring As A Bridge".
Share a single IP address (using DHCP & NAT)
This is one of two options you can choose when you select the Distribute Internet Protocol Addresses checkbox.
When you select "Share a single IP Address (using DHCP & NAT)", the Base Station receives an IP Address from your ISP. The Base Station shares this IP address with the wireless clients through NAT. For more information on NAT see article 58514: "AirPort: What is Network Address Translation?". When you select this option, the AirPort Base Station also acts as a DHCP server and distributes IP Addresses in the range of 10.0.1.2 to 10.0.1.50.
Note: NAT and DHCP are enabled on the wireless interface of the base station only. Configuring the base station to use NAT and provide DHCP service on the Ethernet interface is discussed below.
Ethernet client computers also share a single IP address (using NAT)
When you select "Ethernet client computers also share a single IP address (using NAT)", it enables NAT on the Ethernet network to which the AirPort Base Station is connected. Some cable and DSL (Digital Subscriber Line) ISPs use a 10.0.1.2-10.0.1.254 addressing scheme, so you should leave this checkbox unselected if you use cable or DSL as your ISP.
Note: If your cable or DSL ISP uses IP addresses outside the 10.0.1.2-10.0.1.254 range, you may not cause any issues with their network if you use this option, but you should contact your ISP before you enable this option.
When you leave this checkbox unselected, only the wireless clients share a single IP Address and use the NAT function of the Base Station.
Important: If you leave "Enable DHCP server on Ethernet" unselected, you must manually configure the TCP/IP settings for the client computers on the wired network as follows:
- IP Address: 10.0.1.x (where x is a number in the range 51 - 254).
- Subnet mask: 255.255.255.0
- Router address: 10.0.1.1
- Name server addr: Use the DNS address appropriate for your ISP, i.e. the settings that are being used by the base station.
Share a range of IP addresses (using only DHCP)
This is one of two options you can select when you select the Distribute IP (Internet Protocol) Addresses checkbox.
When you select "Share a range of IP addresses (using only DHCP)", the Base Station is not performing NAT, but instead is distributing a range of IP addresses that are valid for the network to which the base station is connected.
Enable DHCP server on Ethernet
When you select "Enable DHCP server on Ethernet" it enables DHCP services from the Base Station on Ethernet. This checkbox should not be selected if you already have a DHCP Server on your Ethernet network, or if you have a cable modem. This can cause unexpected behavior, including computers losing their connections to the Ethernet network.
Note: Some cable modem ISPs may not be affected by this option. Contact your ISP for more information. Most DSL ISPs are not affected by this option. If you encounter strange behavior, disable this option and see if the behavior persists. Contact your ISP for more information.
When you leave this checkbox unselected, the Base Station provides DHCP services to only the wireless clients.
Note: When you leave this checkbox unselected, you can still take advantage of NAT by manually configuring the TCP/IP settings for the client computers on the wired network. Refer to the section above.
Enable AirPort to Ethernet bridging
When you select "Enable AirPort to Ethernet bridging", all traffic is moved between the wired and wireless side. When this is not selected, for example, a wired client of an AirPort Base Station could not see a wireless client of the base station in the Chooser.
For related information, please see:
Article 106021: "AirPort: How to Set Up Bridging When Using a Cable Modem"
Note: Wireless Internet access requires an AirPort Card, AirPort Base Station, and an Internet service provider, for which fees may apply. Some ISPs are not compatible with AirPort. For more information, see technical document 106590: "AirPort: Requirements for Wireless Internet Access."