So you are migrating from MOM 2005 to 2007 and do not want to go through the hassle of changing your firewall ACLs? Default port for agent to Management Server communication is 5723. To modify it to MOM 2005 default (1270) or any other of your choice, perform these tasks:

• OperationsManager database – this modification is needed for new agents to get properly installed from UI console: GlobalSettings table find the row with value 5723 and change it to your port
• RMS server: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Operations Manager\3.0\Server Management Groups\CPDMGM change “Port” setting
• Management servers: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Operations Manager\3.0\Server Management Groups\CPDMGM\Parent Health Services\0 change “Port” setting
• In case of manual agent install either specify through command line parameter SECURE_PORT=your port or after default install you can always modify it in registry: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Operations Manager\3.0\Agent Management Groups\CPDMGM\Parent Health Services\0 change “Port” setting

Thanks to Anandha Ganesan and Gavin Sharpe ffrom Microsoft or their help and input on this!