It is difficult to answer this queston w/o some more information. To accomplish what you want to do outside of ePO would require some other third party tool or local installation/modification. Insight into what you have in your environment available to you might help us give you some good direction. I have been in your shoes before with a very similar scenario and how I accomplished it was by using SCCM. I created automation that said if this system becomes active/reports in, immediately install Framepkg.exe... (and that EXE would be the one from the new ePO server).
I was thinking that although your server has the same IP address as the old server, it is probably using different agent keys so even though the clients can connect to the same IP address, the keys wouldn't match up and they wouldn't be able to communicate with the new epo server.
The part that confuses me is that you say they are communicating once a month. So if they are communicating once a month, then the statement I made above wouldn't be the problem.
Thanks for advice.
I find out a way to solve this issue without third party software.
What i did is,
1. Installed a RSD in ePO.
2. Deploy Rogue sensor to all network segment.
3. Create a auto response,
Filter: epo server name = Old server name
Action: Deploy McAfee agent