Starting in Switzerland, I would like to take the EuroCity train to Milan through the Simplon tunnel.
For this trip, I have an Interrail pass valid in Italy only. I have to buy a regular ticket for the Swiss part of the route, and the mandatory reservation for the Italian part.
At which station should I split the booking, Brig or Domodossola?
Swiss railcards (half-fare, GA) are valid up to Domodossola, and it is mentioned that reservation is mandatory for all international journeys between Switzerland and Italy. As the stretch between those two stations is the actual border crossing, I would consider it "international" per the definition, and covered by the mandatory reservation.
I find this confusing. Even if travelling on a regular Swiss ticket up to Domodossola, do I need to get a reservation in addition to the one I plan to get for the Italian part?