Paris - Switzerland TGVs indeed are expensive. It is cheaper to leave the train in France and switch to a regional train across the border (see later).

It doesn't work by types of trains but by companies. IC can be found all over Europe and each company has a different policy : 10€ mandatory reservation in France, 3€ in Italy, optional in Germany,…

Seat reservations are not a thing at all in Switzerland, don't bother with it. I've lived here all my life and never made one. Simply hop on and sit wherever you want. As a tip : carriages at the front or back are generally quieter.

Depending on where your hotel is located you have these 3 options :

- TGV Paris Gare de Lyon - Mulhouse 07:22 - 10:02 20€

- TER Mulhouse - Basel SBB 10:16 - 10:40

- IC Basel SBB - Interlaken Ost 10:56 - 12:58 via Bern or 11:28 - 13:28 direct

Option 2 (the one I'd probably choose) :

- TGV Paris-Est - Strasbourg 07:58 - 09:59 10€

- TER Strasbourg - Basel SBB 10:21 - 11:38

- ICE Basel SBB - Interlaken Ost 11:56 - 13:58

Option 3 :

- TGV Paris Gare de Lyon - Frasne 07:56 - 10:42 10€

- TER Frasne - Neuchâtel 10:53 - 11:53

- S5 Neuchâtel - Bern 12:01 - 12:52

- ICE Bern - Interlaken Ost 13:04 - 13:58

"Tight" connections in Switzerland are usual and guaranteed, don't worry about that.

Hello. Noted on this. 

So we just ignore this reservation for IC train on Eurail website?

Also, what do you mean by “guaranteed” here? 

Thanks again

Yes don't bother with reservations in Switzerland.

Guaranteed means that if the first train is delayed the second one will wait for a few minutes. If the delay is too large (unlikely to happen) staff will advise people to take the next train, no more than 30 min later.

I also want to add that timetables are optimized in Switzerland : for example the 14:06 bus to Iseltwald is designed to take people from Basel/Bern, you'll have plenty of time to change. In mountain areas there can be up to 10 buses waiting for the same train to take people to small villages !

The system also works with a clock-face scheduling : all trains come to a station between xx:50 and xx:00 and then leave between xx:00 and xx:10 after everyone has connected. :)

Since reservations are not needed in Switzerland you've got a lot of flexibility. If you've missed a train just add the next one to the app and board. No need to speak to staff in order to get new reservations, etc.

Thanks so much for your prompt reply. We managed to make the reservations.

However, we wrongly put the eurail mobile pass number instead of pass cover number.

Would that be a problem? Worried if the staff reject us to onboard the train, we will travel with toddler so we hope to avoid any issue.

Glad you could make them ! :)

No, it's not an issue as long as names match. Both numbers are valid on b-europe and they don't appear on your reservation (why do they ask for one in the first place... since you have to show both the reservation and app anyway).