Orbi RBK850 & synology NAS - Cant connect to WebDav server from outside the home network

[HelpMeBrah]

I recently upgraded my wifi to the Orbi RBK850 system.  I previously had an apple Airport Extreme.  

I have a Synology NAS connected via Cat6 directly to the Router.

Since changing routers, I can no longer connect to the WebDav server from outside the home network.

I have the ports forwarded correctly and can see that they are open when checking using a service like https://www.yougetsignal.com/tools/open-ports/.

During problem solving, I swap the Orbi system back for the Apple router, and the WebDav is accessible from outside the network again.  So it leads me to believe the Orbi is somehow disrupting access to it, but I cant figure out why.  Does anyone have any ideas?

[CrimpOn]

Truly a puzzle.  Can you please confirm:

• That the Synology has the same internal IP address on both the Apple router and the Orbi router?
  When a port is forwarded through the router, the LAN IP address is critical.
• Do the Apple router and the Orbi router have the same public IP address when connected to the ISP network?
• Is the WebDav connection using the public IP address, or a Dynamic DNS (DDNS) name?

In general, Orbi routers do not respond to connection requests from the internet.  Gibson Research would classify Orbi router ports as in stealth mode.  https://www.grc.com/su/portstatusinfo.htm unless they have been deliberately forwarded by the user.

When one of the "is my port open" web sites claims that a port is open, that means that the connection request has been forwarded to a device on the LAN and the device responded to the connection request.  The Orbi router has no part in the process aside from forwarding requests and relaying responses.

[plemans]

have you checked with synology to see if they require a specific setting or change with your network?
What modem/gateway is the router connected to? 

[HelpMeBrah]

Sorry for the delay in getting back to you, I didnt get a notification that anyone had responded.  Yes, I set the same static IP for the NAS with the apply router and the orbi router.

I double checked, and yes, the public IP is the same for the apple router and the orbi router - I assume this is coming from the cable modem, yes?

The webdav is using a DDNS name - setup by synology - using their service.

[HelpMeBrah]

Synology basically just advises me to make sure I have port forwarding set up correctly, which is kind of a vague generic response it seems....

The cable modem I have is a ARRIS SURFboard SB8200 DOCSIS 3.1 Cable Modem.

[Mikey94025]

Is youtr

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@HelpMeBrah wrote:

I have the ports forwarded correctly and can see that they are open when checking using a service like https://www.yougetsignal.com/tools/open-ports/.

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Is the "Your external address" the same when you use the Apple Extreme vs. the Orbi?  I guess that it should be different because they'll each fetch a different dynamic address from your internet provider.

Next ping your webdav DDNS name.  Make sure that it's IP address matches the "Your external address"  when the Orbi is connected.  If it does not, then that is the problem - How is it updated?  Does something run periodically on the Synology device to keep it updated on the Synology DDNS service?

If the DDNS IP address does match "Your external address", what do you mean by "I can no longer connect to the WebDav server from outside the home network."?  Are you accessing some website or are you running some tool on a computer?

[HelpMeBrah]

Well, for no reason, its all working suddenly today.  It makes zero sense, I changed nothing, but its working.  I dont understand but whatever.

The only thing I have done throughout this process was make a static IP for my NAS and did the port forwarding from within the Orbi Advanced settings about 1000 times.  Im not sure when or why it finally "stuck" but it finally did....

Thank you everyone for your replies.