When installing Data Protector agents, you need to open the port 5555.
To do so, you can just open a command line, as administrator if using Windows Vista or superior and type:
netsh firewall set portopening TCP 5555 “Data Protector”
This will add an exception, and you can deploy your agent.
If you need to do this for a lot of systems, then you should make use of group policy and open this port through Group Policy.
For that type gpedit, don’t forget you need to be a domain admin for this, and look for Windows Settings -> Windows Firewall with Advanced Security ->Inbound Rules
Then right click on the right pane and click New Rule. Follow the wizard to open the port 5555 and apply the policy to the intended OU.