Do I need to generate a certificate for each zenworks primary server in my zone?

I am currently operating on the understanding that the cert was only generated for the 1st primary server in the zone and then as additional primary servers are added to the zone certficates are automatically taken care of at that point by the ZCM software.

During the install of additional primary servers I have to browse and select the selfSigned and Prinate key files. Should I have new files for each server or should I select the files I used to build the first server in the zone?

Please let me know if I am wrong or not.

Thanks in advance.