Hello,
I will get my multisites soon, and I already have a question.

I purchased some domains at one.com , but my hosting is at priorweb

I would like to point all the domains at one (they all have their own directory) to the same master who is at priorweb.

I have the possibility to modify the DNS records on adding A records or Cname, but must I have a fix IP for this at priorweb ?

As it is important for me to have a solid base to work on , I am open to move all the domains to one provider, but some of them are just purchased.

I tried adding a symbolic link but as the directories are not on the same machine this doesn"t work.

So bottom line of this question is : How do manage sites that are hosted outside the physical place of the master. I have seen a lot of videos and read all the manual, but apparantly I missed something in this story.

Everybody is talking about defining the directory of the domain, or adding the domain and so on but I don't have that possibility.

at one.com

I can manage the hosting
manage the dns (creating an alias or forward)

This will be a beginner question, and I apologize for this beginner question.
In attach you find a print screen of the config of dns at one

If your domain are registered at one.com but hosted at priorweb then I suppose that you have setup the domain to have the name server located at priorweb.
If this is the case then the DNS configuration is performed by priorweb and not by one.

You can also do DNS managment from one and setup the A and Cname record as you mention it but if you are using a cPanel system at priorweb, perhaps it would be easier to just change the name server in your regsitrar to let manage the DNS from the priorweb.

Move the domain to another registrar is not required.
As explained when you only move the Name Server to the hosting provider this may simplify your task when the administration tool like cPanel manage the DNS server for you.
So that depends on the administration tool provided by priorweb.

You can not use dns forwarding as this will modify the URL received by JMS Multisites.

The concept of JMS Multsities is to share the files and folders on the disk.
So it is very important to be able configure the priorweb domain in such a way that you can decide where is located your website on the disk.

The title of this post let suppose that you have 2 hosting provider but the description of the post tell that you register the domain in one place and host it in another place.
So we have replied in the scenario where you have a single hosting as it is not possible with JMS Multisites to access different hosting.
The concept of JMS Multisites is to share the same Joomla installation and therefore the same files and folders on the disk.
When you have different hosting, by definition you can not share the files and folders on the disk.