Luxembourg’s Regulator has published to web-based number-portability database look-up portals for the fixed and mobile networks.

http://www.ilr.public.lu/communications_electroniques/numerotation/portabilite_des_numeros/index.html

Or the direct links:

fixed numbers: http://lookuplux.systor.st/lux_lookup_001/lookup.html?lang=4&ism=0
mobile numbers: http://lookuplux.systor.st/lux_lookup_001/lookup.html?lang=4&ism=1