Take note of the ethernet MAC hardware address located on a label at the bottom of your IOLAN+ serial server.
In the Server menu of your IOLAN+, do the following:
1. Set the "Debug mode" to '2'.
2. Change the ethernret mac address to match the one located on the label at bottom of IOLAN+.
3. Save & exit the Server menu.
4. Reboot the IOLAN+.
5. Return to the Server menu again.
6. Set the "Debug mode" to '0'.
7. Save & exit the Server menu.
8. Reboot the IOLAN+.
The ethernet mac address should now appear correctly in the Server menu otherwise repeat the above steps again and if that doesn't work then you may be experiencing a hardware fault with the IOLAN+ which requires