Configuring an iBook Cart, Part 2

- 2002.03.14

This is a multipart series on setting up laptops for use with Apple's iBook laptop cart.

Today's article deals with mechanical issues and configuring the AirPort base station.

Mechanical and Labeling Issues

We purchased eight carts, and for various reasons (mostly related to inventory), it isn't a good idea to swap laptops between carts. The district technicians put the inventory control labels just above the brightness control keys on the keyboards. This is not a bad location. except that you have to open the lid to see it, which wakes up a sleeping laptop.

Further, when students are at work at their desks, you cannot see the the number from your location at the front of the room. For that reason we are recommending a big ol' tracking sticker on the outside lid, oriented so that a teacher at the front of the room can quickly identify which laptop is #12, and so on. Each laptop is to be further labeled so that it says it belongs to cart #2, and the outside of each cart is labeled with a big Sharpie pen or something similar, so if you are returning a lone laptop, it can be quickly returned to its permanent home.

When checking out laptops, we will use this external number for two purposes: first, the laptop lids on sleeping laptops do not have to be opened to get the number the kid signs the laptops out with. Second, we will use Network Assistant to track laptops and will change the machine names so they match the new labels, so it'll be easy to tell which kid is associated with which computer in the Network Assistant setup screen.

I bought a clipboard for each cart just so the checkout lists can have a consistent home.

Finally, in my room we've been having a rash of laptops come out at the beginning of the day totally drained of power. Here are some tips to prevent that from happening:

1. Don't unplug the cart's main power cord at night. Sleeping laptops eventually drain themselves completely. If the iBook has one design flaw, it's that it takes forever to restart after a total power drain. A dead battery is bad. A full battery is good.
2. Sleep between classes; shut down at the end of the day.
3. Make sure that each plug leading to the hidden 16-plug power panel in the back of the cart is firmly seated and that the round adapter that goes into the iBook itself is pushed in all the way. The round housing on these plugs seems to be easily bent, and when bent it will not hold itself in the plug on the iBook as firmly as it should. Often a laptop will get plugged in, but in the process of shoving it into a space also containing the old hockey-puck power supply, the cable would become loose from the laptop. Perhaps the newer square supplies, which are smaller, will not be as hard to fit into one of the slots in the cart.
4. There is a power switch for the main power supply located on the left side on the bottom edge of the panel as viewed from the front of the cart. When yanking cords around you can scrape over the toggle switch and turn it off. (Tell me again why this switch is not on outside of the cart?)
5. Since there are 16 outlets, plus a printer, a hub, and a base station, and only 16 outlets in the cart's power panel, at least one of the plugs in the back must be dedicated to a power strip for the other devices.
6. The back of the cart requires a specialized tool to open. However, a pair of needle-nose pliers will do in a pinch. From the open back panel, you can lift out half the laptops with no big effort. The front panel is secured with a locking mechanism made of aluminum; I can bend it completely out of the way using my thumb. This part needs to be made of steel, and if the back is going to open, it needs a hinged door that can be secured with a hasp and lock. These things are not secure cabinets, folks, so make sure you lock 'em up each night. They are less difficult to break into than, say, a good quality filing cabinet or a chemical storage locker.

AirPort

Now we start to work with the laptops. Each laptop must be configured, but the plan is to set up a "master" laptop that will then be duplicated on all the others. At first we are going to work with one laptop and the base station.

The master laptop should be marked somehow so you don't lose it. It's a pain to pull every laptop out and boot each one to see which one is the right one. I had to do that just today when one class pulled laptops from the wrong cart (I have one in use and one being set up for other teachers).

Make sure the base station is connected to the hub on the cart with an ethernet cable and that the hub's uplink port (usually port 1) is connected to a live port in your room. If your teacher computer is functional, then at least you know its port is active.

In our school many rooms have only one active port, because over the past five years information has been lost, more teachers added since the original opening, etc., and those problems are just now being sorted out. Our IT staff is totally overwhelmed, so they do what they have to do - make the teacher's computer work - and move on. This year more ports are coming online as things slowly get straightened out.

Frankly, these network problems have held back deployment because for the moment we're on fixed IP addresses, and we've been hoping that the promised switch to DHCP addressing would make it easier to configure and move the carts from room to room. As it is, we have fixed IPs, which presents unusual challenges for mobile laptop carts. With DHCP addressing IP addresses are assigned each time a computer is turned on; but it also makes it difficult to track down which machine logged a particular security violation on our proxy server.

Step one - before you even turn on the machine - is to find out the correct network settings for a single new computer on the network. That will be your base station, which will host for all the other laptops. If you're the lone teacher/tech in a room and no one's able to answer your questions right away, then the thing to do is to use your teacher computer settings. If you know how to do it, you can unplug your teacher computer from the wall, plug the base station in the lone working port, and then plug the teacher computer in the hub.

After the base station has the teacher computer's settings, you can tell the teacher computer to use the base station as a router - which is its role for the laptops, anyway - and voilà, everything works and is identical on the school network. The server load on the network should be relatively manageable unless all the laptops are set up as servers moving big video files or something.

Given that you have the correct network settings for a new computer handy - IP address (if fixed), router, mask, DNS server settings, and all the fields in the TCP/IP control panel - you are ready to proceed.

Open AirPort

On the master laptop, do the following:

1. Make sure AirPort is on (AirPort control panel) and connected to the base station.
2. Open the AirPort Admin (located in the Apple Extras folder). By the way, I'm working through all this in OS 9, since there's always that one application your district requires that makes OS X verboten (such as SASIxp.)
3. Select the base station you will be configuring.

Inside the Admin Utility you will find four tabs: AirPort, Internet, Network, and Access Control.

AirPort

1. Give the base station a name, contact, and location. That would be you, if you're configuring it.
2. Give the base station a network name. This should be unique. I'm recommending something like "Base Station for Cart 3."
3. Encryption makes your network more secure. Secure is good.
4. My student Mike Juarez, Who Knows More Than I, says the channel selection is sensitive to local police transmission frequencies and should not necessarily be left in the 1 position.
5. Station density is high.
6. Multicast rate is 11 Mb/s unless your school is all run off of one AOL account or something.
7. Interference robustness needed only if the base station is removed from the cart.
8. Closed network means that users have to type the base station's name to connect. This prevents Joe Public from pulling up outside the school and tapping into the network - at least theoretically.
9. The base station's network password, if used, prompts the users who connect to have a password to use the base station.
10. Optimize placement helps you find the best spot to put the laptops or the base station. Within one classroom, it's not needed. Otherwise, remember: metal is bad.

Internet

This is where you enter the IP address information discussed earlier.

Network

1. Since your base station will be a router, you want to check "Distribute IP addresses."
2. Unless your IT department specifically forbids it for one reason or another, you'll almost certainly be using "Ethernet client computers also share a single IP address using NAT."
3. Enable DHCP server on ethernet lets you use the empty ports on the hub for the non-airport computers in the room. They'll see the base station as a router and share it's IP along with the laptops. If you get to keep the cart, that's handy for servers.
4. Enable AirPort to Ethernet bridging is required to allow the laptops access to the rest of the school network for file servers, etc.

Access Control

Here you can specify which AirPort cards are allowed to use the network. Again, this makes your network more secure. Unless Joe Public happens to know the long ID code embedded in an AirPort card in your laptop collection, he won't be able to connect to the network. He will see the base station, but it won't let him surf or transfer files. This doesn't protect you from a kid who really knows what he's doing, since they can see the card numbers while at school. If you set things up this way, you won't be able to use laptops from one cart on another cart's base station.

This will get you online and ready to fiddle around with the settings on the master laptop. Last week I talked about configuring the multiple users setup for the laptops. Next item on the agenda is configuring proxy servers in the browsers, fine tuning multiple users, and figuring out how the heck kids will transfer files back to your teacher machine before you have to give the cart away.

One reader sent in his own link which details the configuration of the carts at another school. It's good to see this from another perspective, and his article has lots of pictures, too, so take a look at Jim Crittenden's site.

Many thanks to my student and teacher Mike Juarez for explaining the AirPort settings to me. Mike's site hosts his online company that makes streaming servers for Internet radio stations - if that sounds intriguing take a look.