Question about sync to WebDav...

I am trying to set up syncing via WebDav. It works, but…

The issue is that I am running the WebDav server on my home LAN. Internally, I need to connect via the local IP address (:/Share/DevonThinkSync . This works fine for my at-home desktop.

From outside my LAN I obviously need to connect to the external address for my home LAN, so I connect from my laptop via <>:/Share/DevonthinkSync.

So far so good, it all works.

The problem is connecting to the WebDav server from the laptop when I am at home, because I cannot connect from inside the LAN using the external address; my router (an Apple Airport Extreme) does not support NAT loopback.

Therefore, the attempts from the laptop to connect to the WebDav server all fail.

I thought about creating duplicate WebDav locations using the internal IP address as I do from the desktop. Then, when I am on the LAN, those connections would work while the attempts to connect to the external address would fail, while when I am outside the LAN, connections to the outside address would work while the attempts to connect to the internal IP address would fail.

My concern is that duplicating the sync in this manner (I would have two different WebDav syncs set up for the same database) would break the sync process and lead to data corruption.

I wondered if anyone had any knowledge / thoughts on this, or perhaps other suggestions as to how to solve the problem of syncing a mobile computer when the method of connection has to be different when you are inside vs outside the LAN?

NB: I will have the same problem when I try to connect my iPad into the mix with DevonToGo…


What I do is that I have a “split horizon” DNS. I have a DNS entry for my WebDAV server ( On the outside network, points at my router’s public IP and it gets port-forwarded to my WebDAV server. My internal DNS points directly to my WebDAV server.

Thanks…that’s a very good and interesting idea.

Unfortunately, I am not sure how I might conveniently set that up. I cauldron an internal DNS server on my Synology (which is also the WebDAV server), but I would need to figure out how to make that work congenially with my Airport Extreme and the outside DNS servers provided by my ISP which would need to handle everything other than the internal DNS resolution. Ultimately that might not turn out to be as easy or convenient as I would like…

Ideally, (and I am hoping someone from Devon would weigh in on this), if it would not break syncing to just create two different sync connections to the same archive, I would just do that.

Another option I was considering is using the hosts file to control the resolution for this one DNS name, and using a script to change the hosts files depending on which network I am connected to. Also a kludge but probably a much easier one to set up.

Thanks. I had not thought about a split DNS setup, which makes sense, but creates its own set of logistical issues - how to set it up, and of course the maintenance.

My machines get their IP addresses and DNS server info via DHCP from the Airport Extreme. I suspect there will be a way to point that to my internal server (which is at a fixed IP address, of course) where I could set up a DNS server. I wouldn’t even need a split DNS setup, since when I am connected to the internal DNS server I would by definition be on the LAN, and when outside my LAN I would be using the DNS server of whatever network I am connect to at the time.

More food for thought as a solution.

I was hoping someone from Devon might weigh in on whether creating two separate sync entries in preferences to the same WebDAV store would break syncing or not. If it would not, the easiest solution for now is to just do that and let one set of connections fail and the other work depending on whether I am connect to the LAN or outside the LAN.