We've got several machines running Dropbox (all mac osx desktops and laptops - no mobiles / tablet apps). 99% of the time we are syncing data between machines that are in the same room and on the same wifi network, but i dont think its using LAN, just by the amount of time it takes for the data to show up on the other machines.

Is there a way to check if the data is being synced over LAN or back and forth to the Dropbox servers, is there some extra configuration we need to setup to get the LAN working properly ?

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    The files are uploaded to Dropbox first. Then the lan sync is used to transfer the files between your computers. – daxlerod Oct 16 '13 at 19:23
  • what about changes to existing files? in the case of software development, syncing changes to existing files is much more important speed wise than syncing a new file, which isn't too common – Devin Rhode Jul 12 '18 at 20:57
  • Would a change to an existing file first upload, and only after thats done begin doing the LAN sync? – Devin Rhode Jul 12 '18 at 20:58

You can check by using a tool to monitor the network bandwidth for the connections on port 17500 from dropbox.exe to the other computers on your LAN, and then add a large file to your dropbox. If you see data going to the other computer over port 17500, then it's using LAN syncing.

Of note:

If Dropbox detects a firewall preventing access to your LAN, it will turn off LAN sync in your Dropbox preferences automatically. To turn it back on, change your Firewall settings to allow Dropbox access to the Internet and your LAN, then manually turn on LAN sync in your Dropbox preferences.

  • Thanks - you mentioned Dropbox.exe which is a windows application, would this also work on mac ? – sam Oct 16 '13 at 19:13
  • The action (monitoring connections to port 17500) will work on OS X, but the application is named differently (dropbox or dropboxd or something-- I don't have my mac available to check at the moment). – Darth Android Oct 16 '13 at 19:15

Just noticed this if you click on the Dropbox icon then the little gear in the bottom right you get this window popup which seems to indicate that its syncing over LAN.

dropbox LAN sync

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