Finding all available MAC addresses on your network can be a tedious task, especially if your clients are running firewall software that blocks requested initiated from other hosts. Despite that, a quick and easy search on Google.com, e.g ‘LAN MAC address scanner’ will reveal a number of software products that you can use to achieve your desired result.
Other sources from which you can learn your network’s MAC addresses are your switches. If they are managed switches, chances are you can lookup their MAC-Address table. Cisco switches are excellent resources for such tasks as with a single command, they can provide a lot of information.
Another option is your network’s gateway. If your router doesn’t provide such information, you can stick a hub on it and with a laptop computer loaded with packet sniffing software record all packets that enter and exit your gateway.
Hope that helped!.
Previous Memeber’s Answer:
Get the Windows Administrator’s Automation Toolkit book (ISBN 0-7356-2166-7) It has this process as well as many others that might be of interest to you.
The system ARP table will have the MAC address if the device is on the same subnet and has communicated recently with your computer. To get the contents of your local machine’s arp table: arp -a at a command prompt.
As an alternative, if you have advanced switching, go to the switch and find the command to display the mac table. For example, on HP and Cisco switches, sh mac-address will give you all the MACs the switch knows