Quickly gather MAC addresses with ARP

When securing a wireless Windows XP network, in addition to using Wired Equivalent Privacy (WEP) or Wi-Fi Protected Access (WPA) encryption, you can use Media Access Control (MAC) address filtering.

When you enable MAC address filtering, the wireless access point or wireless router verifies that the network card in the computer requesting access has a MAC address in its filter list before allowing the computer to access the network. This means that you must first obtain the MAC addresses of each client computer. To do so, you might think that you have to manually visit each computer and use the Getmac command.

An easier way to gather MAC addresses is to take advantage of the Address Resolution Protocol (ARP) command. Here’s how:

1 - From one computer, use the Ping command to Ping each of the other client computers that will connect to the wireless access point or wireless router.

2 - Type the ARP command along with the -a parameter: Arp -a

When used with the -a parameter, the ARP command displays the ARP cache, which stores the IP and MAC addresses of the computers that most recently accessed the system — or in this case, those computers that responded to the Ping command.

Note: This tip applies to both Windows XP Home and Professional.

View non-present devices in Device Manager

When troubleshooting driver problems in Windows XP, one of the first places you may look is Device Manager, which provides detailed information about every piece of installed system hardware. However, with devices such as removable USB drives, you may need information about devices that are not currently connected; Device Manager recognizes these as nonpresent devices. Here’s how to get information about those devices:

1 - Go to Start, right-click My Computer, and select Properties.

2 - In the System Properties dialog box, select the Advanced tab and click the Environment Variables button.

3 - In the Environment Variables dialog box, locate the System Variables panel and click New.

4 - In the New System Variable dialog box, type DEVMGR_SHOW_NONPRESENT_DEVICES in the Variable Name text box and type 1 in the Variable Value text box.

5 - Click OK twice.

6 - To view the nonpresent devices, go to Start, right-click My Computer, and select Manage.

7 - Click Device Manager, pull down the View menu, and select Show Hidden Devices.

Note: This tip applies to both Windows XP Home and Windows XP Professional.