What's the partition format of your hard drive? Mine is MBR which is working fine, but can only recognize the first 2TB part of the drive.

Maybe it's a compatible issue, tplink router doesn't fully support DLNA media server according to their technicians, which is very disappointing

I don't think this will work. TL-WDR3600 are equipped with 3 identical dual-band antennas. If you replace one with another different type antenna , it's like a chick has one duck-leg, how can it run...

I'm afraid that can't be done. The default routing table of TP-LINK router can't be modified.

Maybe this is the reason why. You didn't specify the target IP address. You can put in the VOIP server's IP address as target IP address.

You may set the access control like this