- Brussels - Paris : the direct Thalys (1h22) has expensive mandatory reservations (32€ 1st class). Or IC train to Kortrijk, regional train across the border to Lille and then TGV to Paris (limited 10€ or 20€) : 2h longer, for example Brussels 07:39 - Paris 11:14

- Paris - Versailles : Eurail Pass not valid on RER trains. There are TER trains from Paris-Montparnasse but way less frequent. Otherwise buy regular tickets.

- Paris - Nice : limited 10€ (or 20€). Book either on eurail.com (website only) : 2€ booking fee per person per journey or https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish (4€ booking fee per order, so could be Lille - Paris + Paris - Nice)

- Nice - Monterosso : a few options

- Nice - Ventimiglia reservation-free

- Ventimiglia - Monterosso al Mare RE trains all the way (reservation-free, quickest way) or IC train for part of the journey (3€ on tickets.oebb.at)

- Monterosso al Mare - Venice : depends on the route (always on tickets.oebb.at). For example :

- Monterosso al Mare - Viareggio 09:07 - 09:58 3€

- Viareggio - Firenze S.M.N. 10:14 - 11:52 reservation-free

- You could spend a few hours in Florence :)

- Firenze S.M.N. - Venezia S. Lucia 12:20 - 14:34 10€

- Venice - Salzburg : best option (15€ supplement incl. seat reservation -> tickets.oebb.at)

- Venezia S. Lucia - Villach Hbf 09:56 - 13:11

- Villach Hbf - Salzburg Hbf 13:16 - 15:48

- Cologne - Amsterdam : reservation recommended, train can get pretty busy. It's free anyway on tickets.oebb.at

tickets.oebb.at will be very helpful to you from Italy onwards. There's no booking fee and it gives free 1st class optional reservations.

For mandatory reservations add Eurrail/Interrail as a discount and select one-way tickets.

B-europe requires pass cover numbers. You can use the pass cover number generator found on the forum. tickets.oebb.at only requires the name of one traveller, nothing else.

Let us know for any other questions :)

In addition to @thibcabe extensive answer:

• Amsterdam to Brussels, for a reservation free itinerary make sure you take the hourly IC to Brussels, not the Thalys high speed train.
• Brussels to Paris is possible to do reservation free, if you go via Charleroi and Maubeuge to Paris via TER. A bit slower, and connections are more limited. About possible about three times a day. It would look like something like this:
  But much cheaper than Thalys of course, and always availability.

It looks like there are engineering works between Maubeuge and Paris on 20th May. At least I couldn't find the connections

Forgive me, I was lazy and didn’t adapt the dates. Seems like engineering works yes. But also two direct TER connections to Paris, from Lille. One in the morning, one in the evening on 20/05.

Like this:

Anyway, key message is: If you have the time and patience for it, and love to see a bit of France with regional trains, there are usually some reservation free possibilities to get from A to B in France :)

Thank you all for the details. Going to sit down on the weekend and start reserving what needs to be reserved. The flights and accommodations have seemed easy in comparison to figuring out the trains, but we travel 6 weeks today, so I need to get them done.

I’m assuming since no one disputed it, avoiding the app for doing this is the right call. Also @thibcabe, prior to using tickets.oebb.at for Italy, Austria and Germany back to Amsterdam, will https://travel.b-europe.com/ help me with any reservations from Brussels through Nice? 
 

Thanks again for the help.

Yes b-europe is the way to go but on 2 separate pages. Here are the links :

https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish (TGV within France, 4€ per order)

https://www.b-europe.com/EN/Booking/Pass#TravelWish (Thalys and Eurostar, 4€ per order)

Thanks for the clarification @thibcabe, I’ve got enough to get me started, possibly with the exception of figuring out reservation-free slower trips through France if we decide to go that route.

bahn.de is usually the best place to prepare your itinerary. It is the most up-to-date.

To see reservation-free itineraries you can either filter and deselect TGV rides or add "via Maubeuge/Kortrijk or xxx other destination"

Don't hesitate for further questions

Thanks again @thibcabe, I think I’m good for now, but you never know what I’ll run into when making reservations. Appreciate the help.

Oh, per my OP for the reservations that do require a pass cover, can I book both my and my wife’s reservations with my pass cover, or should I generate one for her as well?

I think there's no problem using the same number as they do not appear on the seat reservations themselves anyway. But someone will confirm I'm sure

It´s ok to use just one Number The Website ask for that Number to prevent fraud. 

e.g. one of the Reasons that SNCF and Trenitalia used to explain why they stopped to sell reservations via their websites was that it was used often for fraud. People just booked the 10€ or 20€ reservation and thought that they have a valid ticket :/ 

The more important reason being that they don't really like pass holders and can’t be bothered to maintain a booking function for them.

Thank you again all. I think I got through all my reservations successfully, but in the course of booking, a couple new questions arose. Just posting my itinerary again, with reservations and a couple quick questions to follow:

• Amsterdam to Brussels May 16th - no reservation, will take one of the hourly IC trains
• Brussels to Paris May 20th - reserved high speed Thalys, 2:45pm
• Paris to Nice May 24th - reserved TGV, 1:55pm
• Nice to Monterosso May 27th - no reservation, Monterosso-Ventimiglia, then Ventimiglia-Genoa-Monterosso
• Monterosso to Venice May 30 - no reservation options listed (including 3€ per @thibcabe), 2-3 trains per hour
• Venice to Salzburg June 2 - reserved OBB, but didn’t have the option for 15€ supplement incl. seat reservation per @thibcabe . Just 6€ for 2x adult with Eurail Global 1st class
• Salzburg to Munich June 4 - about half the trains were no reserve/reserve options, haven’t booked
• Munich to Cologne June 7 - reserved OBB for 3:28pm, as all trains offered the option and I just like the security
• Cologne to Amsterdam June 8 - reserved a late train, direct, to get the whole day in Cologne

A couple questions:

1. Should there be reservation options on the first leg of Monterosso to Viareggio? If so, I didn’t see it.
2. Venice to Salzburg - Should there be a supplement option? Again, it wasn’t presented one and I only paid 6 for the reservation at 3:50pm, no supplement option.
3. Should I make a reservation from Salzburg to Munich or will there be enough seats to not bother. We’d prefer to use 1st class seats where available.

Finally, one question about actually using my pass. I know we keep the reservation tickets separate and show them when asked on the train. In terms of using my Eurail pass, do I just add the train to the mobile app when boarding, regardless of whether I have a reservation or not? And, are all trains available in the app to add for boarding?

If you have any thoughts on my questions, much appreciated. Otherwise, the assistance has been invaluable. Thanks again.

1. The 3€ seat reservation is for the IC train between Monterosso and Viareggio but there are reservation-free regional trains on the same line not taking much longer. (You'll need the seat reservation for the Frecciarossa train between Florence and Venice but I believe you've done it.)

2. Don't worry the supplement can be bought at any time, even on the train. It should be doable on tickets.oebb.at (15€). It is called Tarvisioverkehr Pass1 (maybe you clicked on "ticket already exists" ?)

3. Lots of trains and capacity shouldn't be a problem. Simply board any train you want (you can always do a free last-minute reservation).

Yes you add trains before boarding (reservations or not). All trains should be available and you can always add one manually if needed.

Thanks @thibcabe. To reply …

1. Monterosso - No, looking up May 30th we have no reservation for that voyage at all on any leg so far. This is a sample of the itinerary and on the previous page there’s no option to pay for a reservation on this leg. Same thing if I use the faster route through La Spezia central, Pisa and Firenze. So, if there’s an option to pay for a reservation, I’m simply not seeing it. I’m not particularly stressed since there do appear to be lots of trains, but just odd that I can’t see any option to pay for a reservation on that route at all. It would be nicer to just know what time I need to be there and have it booked.

   

2. Venice to Salzburg - ‘ticket already exists’ was pre-chosen for me at payment time since I chose ‘Eurail Global Pass discount’ for each passenger for the trip. It never mentions a supplement at all when searching for trains from the initial Timetable & Tickets screen. As long as it’s clear how to get it on the train, that’s fine, but I was just surprised there’s no mention of it anywhere.
3. Good to know Salzburg to Munich shouldn’t be an issue. In fact the Thalys and TGV reservations were the only somewhat expensive ones. The rest were all quite cheap.

Thanks for the advice on the boarding process. I figured it would be pretty simple, and after the first one things should be straightforward. Along with that, I guess taking your first train activates your pass for the allotted timeframe (2 months for us and we’re only travelling for a month, so not a problem).

Cheers.

That's probably because you used the option "Seat reservation only”, which does not work in Italy. You need to add the Interrail/Eurail discount for every person and then select "One-way tickets and day tickets”. Further, the ÖBB website often doesn't work correctly if you want to book multiple trins this way, so you need to book them separately. Finally, the affordable hotels in Venice are around Venezia Mestre and there's an earlier train from Milan to Mestre, at 18:45.

Here again, if you add the Interrail/Eurail account and then select "Seat reservations only”, it will only sell you a reservation. You needed to use "One-way tickets and day tickets”.

Your pass will be activated when you go through the activation procedure. But it's beter not to do that in advance, since you cannot cancel anymore if something unexpected happens after validity has started. If you have a flexipass, then a travel day will be activated when you add a journey to your pass. Here also, it best not to do that in advance.

Thank you @rvdborgt and you are correct. I used ‘reservation only’ because I understood the Eurail pass to be my ticket. So, now a couple questions on that:

• Are the ‘reservations only’ I’ve made no good and I need to go back and rebook them as one-way tickets?
• I think it’s too late to get a refund (not that they’re terribly expensive) or is there a way to add to the reservations that I already have?
• Also, if the OBB site doesn’t work correctly, I’m not at all clear on how to book multiple trains correctly, since my trips do use multiple trains to get to my destinations. It sounds like you’re saying that once I see the train trip and connections I want to take I’d need to search each of those legs individually and add one way tickets. That seems, uh, cumbersome.
• We are staying on the Santa Lucia side of Venice so that’s the better station for us.

I figured adding anything to the pass risked activating it, and once I’ve added a train when we get to the station, it’ll just be the same thing each time we take one.

No need to do that. I agree that the ÖBB website is not really intuitive for making reservations.

In principle though, the discount method should always work and that should also result in optional reservations free of charge.

Unfortunately, it currently works this way for Italy. You can try to get them in one go, but there's often a message saying it can only give a price for part of the journey, although it normally works fine if you book trains individually.

Thank you again @rvdborgt. Hopefully I can wrap this up with one more response and clarify what I have left to do. If I’m understanding everything above  ... 

My reservations for Brussels-Paris and Paris-Nice should both be fine, as should my reservations from Munich back to Amsterdam through Germany. Not seeing any need to reserve Salzburg to Munich.

Italy - I have not reserved any seats so far from Nice to Venice:

• Nice to Monterosso - No reservations needed, even from Ventimiglia onward? I’m assuming the train passes through Monterosso first, so nothing on the trains between the Cinque Terre villages, or La Spezia central back to Monterosso?
• Monterosso to Venice - Using one way tickets, yes I can see what you mean, certain legs with connections, but not end-to-end. Fees are anywhere from 6E to 20E on per leg. ie, Monterosso to Milan on the longer trip or Firenze to Venice on the shorter trip. I guess I really wonder if we’ll be fine as walk-ons, or I should reserve individual legs. Per the image below 20E seems pretty steep to only reserve Firenze to Venice.
• Venice to Salzburg - Looking at my reservation timetable, I have seats on both legs from Venice to Villach and Villach to Salzburg, so that’s good. Just need to add a supplement and can do so at the station or even on the train?

It’s really the trips from Nice to Monterosso and Monterosso to Venice that I need to decide if I should reserve, based on possible demand. 

30th May shouldn't be particularly busy and as you said yourself there are multiple options.

The reservation fees in Italy are as follows :

- 3€ Intercity train (IC)

- 10€ high-speed Frecciarossa train (FR)

10€ is the same price as a French TGV so I don't think it is that much (of course still a shame to pay for these seats). No matter how long the ride is, prices stay the same.

Ventimiglia - Monterosso can easily be done reservation-free using regional trains (RE or R). If there's an IC for part of your route then you'll need to pay 3€ but it can be avoided by taking regional trains (deselect IC trains on bahn.de or any other planner).

Monterosso - Venice has 2 main routes as you said :

- Monterosso - Milano (3€) - Venice (10€)

- Monterosso - La Spezia - Viareggio - Florence - Venice (10€)

Much better via Florence as you wouldn't have done that route a few days earlier.

Thank you @thibcabe and not only is the route through Florence better, but it appears to be faster. So, it sounds like ... 

• I won’t worry about any reservations from Nice to Monterosso.
• I’ll take the Florence route from Monterosso to Venice, and I guess I’ll have to note the stops and search individually to reserve. I’d hate to reserve the last leg and miss it because I got delayed on earlier legs.
• Just to have it sorted, wondering if I should get the supplement in advance or just hit the desk at the station before we travel.

I really do appreciate all this help, particularly since this is effectively one massive train tour. I honestly don’t know how people could plan this kind of trip without advice on these forums. Seems like reservations across the companies and regions still needs some work for the benefit of customer experience.

Monterosso - Venice : if you're worried about missing the reserved train, you could leave Monterosso early, leave your luggage at Florence train station and then spend a few hours walking across the city before taking the last train. The train station is really close to the city center. It's an easy 10-min walk between the station and the famous Dome, a bit more to Ponte Vecchio. Just an idea ! :)

Via Florence you'd only need seat reservations for the last high-speed train from Florence. Otherwise the first leg can easily be done using reservation-free regional trains.

You could buy the supplement right now for peace of mind, it won't cost anything more.

I’m liking this idea a lot  as, aside from travel between cities, we generally walk everywhere and love it. Our travel plan is generally mid-afternoon and later trains, to get most of the last day in any given place we’re staying, but getting a couple hours to walk around Florence a bit would be very nice (gathering Firenze is Florence on the trains).

Agreed. I’m a planner by nature and prefer this. I’ll just do the reservation process again, but choose one-way tickets instead of reservation-only, and get the option to buy the supplement, while just keeping the reservation I already have? I gather supplements are a thing for travel between Italy and Austria, in this case?

Oh, and I think I read at one point that supplements are needed to/from Italy, but I never saw that doing seat reservations only searches. Do I need a supplement on the Nice to Monterosso route AND Venice to Salzburg?

Florence (or Firenze in Italian indeed) is really worth a stop yes. So if you can spend a few hours there, why not !? :)

These supplements exist between Italy and Austria (Brenner and Tarvisio lines) because the company running these lines isn't part of the Eurail/Interrail scheme and would like to receive "some money" too, so to speak.

EDIT : No supplements between Nice and Italy, it's only between Italy and Austria, don't worry.

Or so they claim. That supplement may have started because of that reason, but times have changed. If companies like Regiojet and Westbahn can get their share of the pass revenue and don't need to charge additional supplements, then surely others can also do that. And maybe they already do, but just keep the supplement in place because it's easy money.