1. Start Inventory Manager.
2. Select 'Export Serial Numbers' from the Tools menu.
3. Once the information is gathered you can click the Export button to save into a file.
From Extreme Management Center:
1. Change to the Network > Devices tab.
2. Change to the By IP list.
3. Right click on the Top level of the tree that list the total number of devices and select Configuration/Firmware > Register/Export serial numbers