Enabling external FTPS access to ReadyNAS 214

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geojay wrote:

I'd like to understand why this is required, whether there is any risk, whether I need to change any config on the NAS and what I need to do on the router?

 

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FTP has a control port (21 by default) and passive ports for data transfer.  So you do need to forward passive ports.

The first thing is to figure out how many passive ports you need.  I always recommend 4 passive ports per simultaneous user.  So you expect 3 simultaneous users, you'd need 12 passive ports.

The recommended range for dynamic ports is 49152-65535, so (in this example) you'd need to pick 12 ports in this range.  For instance, 54321 to 54332.

Then you set the passive port range on the NAS to this range, and forward them in the router (as you did for port 21).

As far as risk goes, you do want to be cautious when forwarding ports.  In this case you are depending on the NAS to properly reject attempts to hack into the NAS using these ports. I think the risk is pretty low.  

You should set the NAS to require FTPS, and make sure you are using strong NAS passwords.