If you are running multiple central administration web applications in your WSS or MOSS farm (e.g. central admin application on the index server and WFE server) for central administration redundancy and high availability scenarios, how can you find the first server configured in the farm with the central administration site? Many times you need to know which server was built first in the farm and in most cases, server running the central administration site is configured first in the farm. In cases like multiple central administration site, things get tricky. In situation like this, follow following steps to find out which server was built first by knowing which central administration web application was provisioned first?
Log on the each server in the SharePoint farm and access the Central Administration Site from the Start menu. All of them should take you to the only one Central Administration Site regardless of how many central administration web applications are provisioned in the SharePoint farm. This is the central administration web application was installed first in the farm and server used to create the farm.
NOTE: This configuration can be changed in the registry.
Hope this is helpful…