Site mirrors with sessions

I am currently working on a web crawler and came across a question.

The website requires a login and has multiple mirrors of the same site. Since i'm handling the cookies/sessions part, I wanted to know if there is a trick to alter the cookie and make it work for different mirrors of a site without having to login again

I'm guessing it is not possible since the server on a given domain is handling its own sessions and aren't shared across different servers.

Any ideas?

Thanks for reading me