Trains that REQUIRE an additional reservation fee
Trains that DON'T REQUIRE an additional reservation fee
InterRail - Reservation and supplement - Luxembourg
To travel with certain trains you need extra reservations despite your Interrail pass. Find here on Raildude the information about where to make these reservations and how to avoid them.
InterRail | Reservation and supplement | Luxembourg
The following types of trains require an extra reservation or extra charge.
A reservation always includes the extra charge and the seat reservation.
Note: the given prices may vary due to service or handling fees. Depending on whether you purchase the reservations/tickets online, at a ticket machine or at a railway station.