Reading the MAC address sticker:
The base of the NSLU2 case has serial number and MAC address barcode stickers. The MAC address is shown in the form
Thus, a better way is to boot the NSLU2 while running "arping -f 192.168.0.1", as described on the TelnetIntoRedBoot page. As soon as the arping command completes, you can see the MAC address in the output of "arp -na | grep 192.168.0.1". Then, verify that the last three bytes correspond to those on your sticker.
On my NSLU2_UK box, use a browser go to http://192.168.1.77 and enter the admin screen. Select the 'Status' menu option and at the bottom of the window select the 'details' button. This will produce a screen including the MAC address information
Hardware Address: aa:bb:cc:xx:yy:zz
Where xx,yy and zz are the details on the bar-code sticker and the full MAC address is aa:bb:cc:xx:yy:zz