Hi Atreya,
OME inline help contains ports and protocols table which will guide you through the ports you need to open on management station(where OME is installed) and managed nodes(the target servers).
The port tables are located under Managing security settings->Supported Protocols and Ports section.
For in-band updates(using OMSA) you will need port 135 on managed nodes for windows targets and 22 for Linux targets.
For out of band updates (using iDrac) you will need port 1278 and 1279 on management station and port 443 on managed nodes.
Ftp port 21 is needed on management station if you are downloading catalog and updates from Dell ftp website.
Regards
Abhijit