Train from Barcelona to Montpellier (buy tickets online?)

I've found one route I'd like to take to get from Barcelona to Montpellier on the DB Bahn site. It's on a Sunday (April 28), so the options are more limited. Barcelona Sants to Cerbere (Regionalzug) Cerbere to Narbonne (Regional-Express)
Narbonna to Montpellier Saint-Roch (Regional-Express) This route does not appear at all on the RailEurope site. I've never traveled in Europe and I'm completely confused about the trains. Is it because these are regional trains? Are these available online anywhere for purchase? Should we worry about this route being booked? We will be doing a limited amount of train travel (we will be renting a car for a few days) so we will not be purchasing a pass. Also when a train says compulsory reservation, does that mean it must be booked ahead of time (weeks in advance) or can it be done at the time of travel? I'm seeing compulsory reservations for a trip from Nice to La Spezia. Any advice would be much appreciated!

Posted by Philip
London, United Kingdom
2881 posts

Tickets for Regional trains in Spain cannot be purchased online at all, and tickets for Regional Express trains in France don't have any significant discount for advance online booking, so I'd purchase tickets at the stations. You may have to buy a new ticket at Cerbere instead of purchasing for the whole journey in Barcelona. Compulsory reservations don't have to be booked in advance, you can buy a reservation on the day unless the train is totally sold out. This is unlikely to happen, but it might if, say, it was the Friday before or Monday after a holiday weekend.

Posted by Tim
Minneapolis, MN, USA
8700 posts

For Nice - La Spezia you will have to change trains in Ventimiglia. SNCF (French National Rail) will sell you a ticket on a regional train for Nice - Ventimiglia, but probably not for the leg(s) totally outside of France. You can buy tickets for Ventimiglia to La Spezia at the station in Ventimiglia. If you book either IC trains or ES trains well in advance (up to 120 days allowed) on, you can get a Super Economy fare. You cannot book regionale trains more than a few days in advance and there is no discount for advance purchase.

Posted by Harold
New York, NY, USA
5756 posts

Your post illustrates why everyone here discourages use of Rail Europe's website - they don't list all trains, while the Bahn does.