You have to install and configure your network hardware before installing NoCat. There are three basic areas you need to work in: the AP, the Linux box (including configuring the two Ethernet cards), and the WAN connection (which I will assume to be DSL, for this discussion).

The basic hardware setup looks like that shown in Figures 10-3 and 10-4. It involves three boxes: the wireless AP, the Linux gateway and the DSL “modem.” One Ethernet card connects to the DSL modem. The other Ethernet card connects to the AP. The names assigned to the Ethernet cards in Linux (“eth0” and “eth1”) are typical. However, you can assign any names you want (using System Settings, Network in Red Hat).

If you don’t already have your DSL working, it’s probably best to make sure that things are at least minimally functional on the Linux side first. Then get the Linux box talking to the WAN.

Finally, add the AP into the mix.

To set up your NICs on the Linux box, click on the red hat and go to System Settings Network. A minimal requirement here is to have two active NICs. If one or both are either not on the list or inactive, things are not going to work. In addition, the status should be ok.

If one of the cards is inactive, try clicking Activate. It may activate, or you may get an error message giving you a clue about what is wrong.

If one of the cards is not on the list, click the New button and use the installation wizard to install it. If nothing else seems to get a card working, you may want to try deactivating, deleting, and reinstalling the card. It only takes a few minutes, and it’s a low-risk operation, if you make sure to write down all the information necessary for reinstalling. So, before you delete a card, write down all the information in all the tabs on the Network Configuration screen (Devices, Hardware, IPsec, DNS, Hosts), as well as the information available by clicking the Edit button.

The procedure for installing a card is as follows. Click the New button. Select “Ethernet connection” from the “Device Type” list, and click the Forward button in the lower right. Hopefully, on the “Select Ethernet Adapter” screen, both your cards will be there in the list, making it easy to select them. If not, click on “Other Ethernet Card” and choose from the drop-down menu based on your knowledge of the manufacturer and model of the card. Do not worry about the empty boxes in the “Resource” section, or the “Unknown IRQ.” Although you can set these things manually, they usually auto-configure correctly. Click “Forward.”

The information you enter on the “Configure Network Settings” screen will be crucial to making your NoCat server work correctly. One potentially easy way out is to accept the defaults, “Automatically obtain IP address settings with dhcp,” and “Automatically obtain DNS information from provider.” If this works, fine. If not, you can go to System Settings ➪ Network ➪

Edit and try something else. If you end up having to set static IP addresses (because automatically obtaining them doesn’t work, for whatever reason), there are many right ways, and probably more wrong ways, to configure your network.

Here are three general principles you should be aware of:

1. You can’t successfully configure your NICs in isolation from the other components of your network. Thus, network setup may be an iterative process, in which you tinker with one part of the network (such as AP configuration), and then go back and change other parts of the network (such as NIC configuration) to make them compatible.

2. No two devices on your local network can have the same IP address.

3. Each NIC must be configured to talk directly to the network device to which it is connected. That generally means being in the same Class C network. In terms of IP addressing, that means that, of the four sections of the IP address, the first three are the same. For instance, if the IP address of your DSL modem is 192.168.1.1, the NIC that connects to your DSL modem will have an address like 192.168.1.XXX, where XXX is a number from 2 to 254. (It can’t be 1 in this case, because that’s already taken by the DSL modem.)

The default gateway is the address of the next device in line along the path to the Internet. Figure 10-5 shows one possible setup for IP addresses and default gateway addresses for the AP, two NICs, and the DSL modem. DNS permits “resolving” domain names like www.google.com into IP addresses. Thus, getting the correct addresses for the DNS servers is crucial for making things work. If you use your provider’s DNS servers, you should be able to ask your ISP what IP addresses are for the provider’s DNS servers. Or you may get the DNS server addresses automatically using DHCP.

hat ➪ System Tools ➪Terminal) and type service network restart. Any time you want to check the settings of these cards, go to the command prompt of the GNOME terminal(click on the red hat ➪ System Tools ➪Terminal) and type ifconfig.

Once your NICs seem to be configured correctly, open the browser on the Linux box and make sure you can access both the DSL modem and the AP. You do this simply by typing the IP address of the device in the address bar at the top of the browser. You should either get instant access to the device, or else a login screen.

If you get an error such as “connection refused,” the problem could be a bad cable, a loose cable, or a crossover cable used where a standard cable is required. Or you may have violated rule number 3, as discussed above. You could also have connected to a bad port on the device.

If your service provider has turned your service on, and it is properly configured on their side, you should be able to follow their instructions and get things working. One possible wrinkle is that you may prefer to run DHCP on your Linux box, whereas the provider’s instructions may assume that the DSL modem will be the DHCP server. Remember that you should not have two DHCP servers accessible to any DHCP client. So, if you are using the Linux box for DHCP, you should turn off the DHCP capability on the DSL modem and the AP.

If the Linux box and the WAN device are configured correctly, you should be able to browse the Web from the Linux box. If you can’t, see if the lights on the front of the DSL modem indicate a good WAN connection and a good Ethernet connection. Use the browser to access the DSL modem and check out its status screen. If everything seems OK on the DSL modem side, then you probably have a problem in the Linux box configuration.

With many APs, the recommended setup is to put the AP in bridged mode and use a crossover cable to connect to the Linux box. However, what “bridged” means here is simply that the AP is transparent to the IP network, acting as a simple Ethernet bridge. For example, your clients would not use the address of the AP as their default gateway. Instead they use the address of the Ethernet card that is connected to the AP. Clients essentially do not see the AP. Instead, they see through it to the Ethernet card.

Unfortunately, terminology is not consistent among AP manufacturers or models. The Linksys WAP11, for instance, has a “bridged” mode in which it can only talk to other Linksys WAP11s. Do not use the bridged mode on the Linksys WAP11 for this project. The Linksys WAP11 is inherently a transparent Ethernet bridge and does not need to be put into any special mode to act that way.

When you’re buying an AP for NoCat, the simpler, the better. If you have a more sophisticated AP, set it up in its simplest mode. For example, the AP may have a “gateway” mode, which would be preferable to a “router” mode.

Whether you should use a crossover cable depends on how the AP port you are using is wired. On the WAP11, you should always use a crossover cable when you are not connecting to a hub. Since you are connecting directly to a NIC in this case, you would use a crossover cable with the WAP11. Some APs have both crossover and “straight” wired ports, and you can generally use either one, as long as you use the right kind of cable with it. You can usually tell whether you are using the right kind of cable by looking at the lights on your AP, to determine whether it is seeing a good Ethernet connection on the port.