Switch between Asterisk servers

I have such infrastructure:

Ast1 (provider 1) - IP1
Ast2 (provider 2) - IP2

Softphones on client computers with configured two IPs to two Asterisk servers. User has to manually switch between each server.

I need to change this that user will have only one account configured (eg. IP3) and on IP3 will be an application to forward call to Ast1 or Ast2. So IP3 will be something like a proxy server. Is it possible? If not, what is the best way to manage traffic without modifying dialplan?

You could do it with a proxy or with Asterisk.

Could you give me some details?
With a regular proxy I probably couldn’t set: comp1-5 call via Ast1, comp6-10 via Ast2
Do you know any transfer application based on the rules?

comp1 --------> PROXY SERVER -------> Ast1
comp5 --------> PROXY SERVER -------> Ast1
comp6 --------> PROXY SERVER -------> Ast2
comp10 -------> PROXY SERVER -------> Ast2