Are you travelling with a rail pass (you’ll need to make reservations if so) or do you need to buy tickets?

You can take a Euromed train from Alicante to Barcelona, then another high speed train to Montpellier.

Edit: it looks like there is only first class available on the Alicante-Barcelona trains tomorrow. First and second class is available on the second leg.

Yes, we have Global rail passes, 1st class.  On the rail planner it tells me 3 legs to make the trip.  I don’t see the Euromed in the list.   Is it best to wait until I get to the station to reserve?  

Make sure you’re searching for Montpellier Saint Roche, rather than Montpellier Sud de France. Try searching for each leg individually.

First Alicante-Barcelona Sants, departing 0655 or 0915. Then Barcelona Sants-Montpellier Saint Roche

You can make reservations at Alicante station tomorrow morning. You might be able to make them through Eurail now.

You also have the option of going via Madrid. That’s the 0940-1950 in the screenshot above.

Both Euromed have a single 1st class seat left. Not gonna work unless you split.

I'll have a look at options. I'm sure we'll find something. Are you 2 people?

Flexibility in summer is really hard, especially in countries with mandatory reservations such as Spain and France...

Alright so the first Euromed is now sold out and the second will be soon. Travelling via Madrid is your only option.

Book the 08:35 or 09:40 AVE to Madrid-Chamartin now on eurail.com. There are plenty of seats left.

Go to Alicante station early tomorrow morning and queue at the ticket counter. Ask if they can sell you Madrid - Montpellier reservations -> unlikely they can as there's no seats left all the way. However by splitting reservations in Barcelona it should work:

- AVE Internacional 9725 Madrid-Puerta de Atocha - Barcelona-Sants 13:25 - 16:22 -> 6 2nd class seats left (Basico)

- same train but new carriage/seats

- AVE Internacional 9725 Barcelona-Sants - Montpellier St-Roch 16:34 - 19:50 -> 12 1st class seats left (Elige Comfort)

Staff should speak English. Feedback much appreciated. Feel free to ask anything.

Fortunately things will be much easier once you're out of Spain and simply fantastic in Switzerland.

To sum up:

- go to Alicante train station at around 7:30

- AVE Alicante-Terminal - Madrid-Chamartin 08:35 - 11:08

- any suburban train to Madrid-Atocha (follow the Cercanias signs)

- lunch break

- AVE Madrid-Puerta de Atocha - Montpellier St-Roch 13:25 - 19:50

Otherwise I'd look at Flixbus, Blablacar, ALSA or similar until Barcelona. EDIT: too complicated.

Travelling in peak season on a route with few trains is kinda hard.