Hi I am trying to setup FIM2010 between 4 different forests. I have it installed on one site. However I am unable to resolve other forests because only limited number of nodes are accessible between them and there is no trust. Would you please what firewall ports need to be openned between physical sites to accomodate FIM? I assume port 53 between DNS servers so I can setup the conditional forwarding from FIM site but don't know about the rest. I appreciate your help.

Here's a link to the ports and protocols needed for various Management Agents, including Active Directory http://technet.microsoft.com/en-us/library/cc720599(WS.10).aspx

Thanks but that does not tell me the ports needed for "Gal Sync" / "Synchronization Service" which I believe is needed for creating contacts on the opposite forests :-( Would you please be more specific? Thank you

You definitely need 389 open between sync server and all environments participating in this process. Unless you have local DNS, you would need 53 open as well. If the target Exchange versions are 2003, then this should be sufficient. If you are using 2007 open, you will need RPC(135) to be reachable from sync server to CAS server for Exchange.