Quickly gather MAC addresses in Windows XP 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.

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