Configuring Advanced AirPort Features

AirPort has a few more tricks up its sleeve, mostly in the realm of providing greater control over network settings.

The Show All Settings button in the Airport Admin Utility displays all of the base station's settings, organized in tabs. If you're familiar with older versions of the AirPort Admin Utility, you'll notice some changes in version 3.1 and above. The most obvious change is the addition of a WDS tab, which groups all the features related to wireless bridging.

AirPort Tab

All WDS configuration information has been moved off the AirPort tab. Also, the AirPort tab has a Channel pop-up menu and a Wireless Options button that opens another configuration sheet.

You can let the base station automatically choose its own channel not taken by other wireless networks in its detection range. But if you are bridging base stations, manually choose a specific channel for all.

The Wireless Options configuration sheet looks like this:

The Wireless Options configuration sheet gives you control over three settings:

• Multicast rate: This sets the minimum speed at which the base station transfers data. The higher the multicast rate setting, the shorter the range. If your AirPort network has certain audio/video streaming servers or other applications with multicast capability, you can control the quality of the transmission by setting the multicast rate. If you set the multicast rate high, only clients on the network that are within range and can achieve the speed you set will receive transmissions. You can set the multicast rate to 1 megabit per second (Mbps) to extend the range of your network beyond the default.

• Enable interference robustness: You may experience network performance problems if a microwave oven or other source of interference is used frequently near your base station. To minimize interference, turn on interference robustness. Client computers with AirPort Extreme Cards must choose Use Interference Robustness from the AirPort menu extra. Client computers with earlier AirPort Cards will already take advantage of the feature. The farther away the interference source, the less likely it is to cause a problem.

• Transmitter Power: Use this option to scale back the transmission power of your base station to limit the range in which wireless clients can connect. It is available only with AirPort Extreme and AirPort Express base station models. The Transmitter Power control can only decrease the base station's range. That's useful for narrowing the wireless range to avoid interfering with your neighbor's network—or to avoid providing your neighbor with free Internet access. Be aware that the slider provides an estimate of the power level; it's not exact. Also, every environment is different, so you may have to experiment until the transmission power is set to your satisfaction.

Network Tab

On the Network tab, under “Share a single IP address (using DHCP and NAT),” there is a pop-up menu from which you select the private IP address range to use when providing IP addresses to computers connected to the base station.

In older versions of AirPort software, the IP address range hosted by the base station was set to the 10.0.1.x range. Now you have three private IP ranges to choose from:

The default is 10.0.1.1 addressing. If you choose 192.168.1.1 addressing, for example, Dynamic Host Configuration Protocol (DHCP) clients will get a 192.168.1.x address when they connect to your base station.

You can also customize these ranges slightly to provide compatibility when adding a base station to an existing network. Choose Other to open the following dialog:

Here you can change the third octet of the private address base. You have the same three base IP sets to choose from in the “First address” field:

Here are two examples of how the private addressing scheme works.

• If you enter 5 in the preceding dialog, your private IP address would be 10.0.5.1, and the DHCP addresses offered by that base station would be 10.0.5.2 through 10.0.5.200.

• If you set the address to 192.168.10.1, your DHCP addresses would range from 192.168.10.2 through 192.168.10.200.

Remember that the three officially designated private IP address ranges, 10.0.x.x, 172.16.x.x, and 192.168.x.x, cannot be used for computers connected directly to the Internet—they can be served only to computers on private networks that are behind Network Address Translation (NAT) routers.

WDS Tab

The WDS tab makes setting up WDS networks simple. When you first open the WDS tab, it looks like this:

The pop-up menu next to the “Enable this base station as a WDS” checkbox has three items:

• Main base station: This is the base station that is connected to the Internet and is sharing its connection with remote and relay base stations.

• Remote base station: There can be up to four base stations connected to and sharing the main base station's Internet connection.

• Relay base station: This is a new type of WDS base station. It connects to the main base station and shares its Internet connection with remote and other relay base stations. It is a remote base station with DHCP and NAT active—in effect, a fusion of a main and remote base station.

Here are examples of what each kind of base station can do:

• A main base station can have up to four remote or relay base stations connected to it.

• A remote base station can be associated only to a main or relay base station.

• A relay base station can be connected to a main base station while having remote base stations connected to it.

You can use the WDS tab to configure multiple base stations in a single set of actions. For example, to set up a main base station and four remote base stations as a WDS network, you can configure the four remote base stations just by configuring the main base station, without having to access them separately.

You configure the WDS tab in two steps:

At the top of the pane, you activate WDS and choose the type of WDS base station you want this base station to be. The options below the checkboxes change to reflect the base station type.

When you choose “main base station,” the screen looks like this:

Your options are to allow wireless clients on this base station, and to scan for base stations and wireless networks to use as WDS remote base stations.

The “remote base station” menu item displays these options:

You can select “Allow wireless clients on this base station,” and you must enter the AirPort ID for the main base, either by typing it in or by clicking the Select button and browsing for it.

The “relay base station” menu item displays these options:

Notice that there are settings for both main and remote base stations.