I have a Drobo 5N I use for Mac Time Machine backups and file sharing. After installing McAfee on my Mac and opening the required ports for Drobo my Mac cannot see the Drobo 5N and perform its backups. Odd thing is that when I shutdown the McAfee firewall everything goes back to normal.
So question is am I missing required ports or is McAfee just not playing nice?
Sort answer: if you tell us which ports you opened up we can tell you whether you are missing any.
Long answer: I’m not sure which version of McAfee you’re using but I used to use the free version of Sophos Antivirus for Mac and I found it more trouble than it’s worth with its large memory and CPU requirements. Not wishing to appear complacent, but there has never yet been a real virus written for OS X (plenty of other malware, including spyware, but no actual virus). Some say it’s impossible to write an effective virus for OS X, and not just Apple fanboys. Me? I’m not so sure. OS X is essentially UNIX, with a pretty user interface and Apple his tight control over it and over the hardware on which it runs. It’s robust but UNIX has had its fair share of viruses in the past and it would be foolish to believe that all the holes have been plugged, but I think it’s fair to say that the risk is much less than with Windows. My suggestion is to get rid of McAfee, as I did Sophos, and reclaim the memory and CPU cycles it uses. Use the firewall that’s built in to OS X if you feel the need (opening up the Drobo-specific ports) and if you want an application that can be run manually from time to time to scan for malware you can download ClamXav from the Mac App Store for free. You run it when you need to so, not being memory resident, it only occupies hard disk space.