Why is LAN sync not working?

[Justin Dave D.]

Hi. I'm wondering why Drobox's LAN Sync feature is a hit or miss, at least for me. Sometimes it would download the files through the internet despite being on the same network with my other PC. I've done the following already:
- Allow Dropbox through the firewall, I even tried disabling the firewall of both PC
- Port-forward 17500

Anyone experienced the same and was able to solve the issue? Thanks!

[Tom_H]

What you may be seeing is that the LAN sync is working, but the file is being checked against the database online. I often see it checking against the database. Usually the inly time I ever actually notice LAN sync in the UI is when its a larger file type.

• Also the file is first verified to exist online and only then is LAN sync is triggered. The server is what tells the apps to LAN sync.

[Justin Dave D.]

Hi, Tom. I've actually left Dropbox to sync for hours hoping it would switch to LAN Sync, but to no avail. Thanks.

[Chris G.2]

I found that pausing sync for a minute and then restarting sync triggers the LAN sync. I suspect the "LAN discovery" is using multicast DNS and therefore is a little wonky sometimes.

[Daniel B.41]

Wait a minute... If DropBox needs to push the file to the server BEFORE it synchronizes with local machines, doesn't that kinda defeat the purpose of LAN sync? It should notice that one machine has a file to share, make a note of it in the online database, share the file locally, and THEN upload to DB.com. I hope I'm missing something here but, if any other service does it more efficiently, that's enough motivation for me to switch.

[Ken W.4]

I'm seeing the same thing, have done for the last year. It's driving me nuts.

At the moment I have a MacOS desktop computer that's fully up to date, a Windows laptop that I just booted up which is a couple of weeks out of date due to being turned off, and a Windows desktop that I just connected to my Dropbox account.

My 64 GB Dropbox folder includes lots of photos and other large files which are perfect for LAN sync.

However, both Windows machines are downloading all the files from the Internet instead - very slowly, and eating up all my Internet traffic allowance.

I saw the laptop using LAN sync briefly, 2 days ago, but before and since it has used only Internet download. Both machines are estimating 12-20 days to finish their sync.

I've used Wireshark to look at the network traffic, and I can see all 3 machines exchanging LAN sync protocol messages just as you'd expect. However, no significant part of the file updates are being done via the LAN.

I've previously logged a support ticket on this issue and got no useful help at all.

Frankly I think this feature is a dud and I'm completely frustrated, to the point where I'd dump Dropbox for more reliable software if I could find it. Can anyone recommend an alternative that provides similar features, including robust LAN sync functionality?

[Tony K.16]

How do you know LAN sync is even working? I just setup a new (old) computer at my house with a 1Gb/s network. 60GB of dropbox data took two days to update this new machine. Of course the other two PCs were fully up to date, so I would have expected 'lan sync' to be much faster. This doesn't seem well implemented at all.

[Rodrigo F.12]

LAN Sync indeed does not work anymore with stable Dropbox builds. THEY know that, but THEY just don't acknowledge the problem. Shame on you Dropbox!

Ref: https://www.dropboxforum.com/hc/en-us/community/posts/204363859-LAN-Sync-does-not-work-

[Carole R.4]

Same problem here with Windows computers on versions 3.8.8. Sometimes it works sometimes it doesn't, Firewall is turned off, on a Business environment this is not reliable at all. 

[Loris A.]

Lan sync never worked for me. i'm using now Win8.1 (DB 3.8.9), firewall open, port 17500, 17600 ,17603, 80, 443, open (tcp and udp, since is not specified anywhere), connected on same subnet with
Centos 7 (DB 3.8.9), using dropbox.py lansync y , firewall open for entire subnet, sharing subnet with
Windows 10, DB 3.8.9. Firewall open (inboud/outbound) for port 17500,17600 and 17603, 80 and 443 (tcp and udp).

two (Centos and W8.1) of 3 box was up to date before installing DB over Windows 10 ....and with LANSYNC active.
Last box installed  (W10) does not sync with lan. Doh! :'(

I think Sync Over LAN need some tuning or a new howto.

Doh! :'(