Problem with NAT Loopback

[AlexKalopsia]

Hi everyone, I am having a problem with the local loopback on my A66U.

I reach my NAS via https://nas.mydomain.com from within my local network. I now realized that if I try and upload some files via http://mynasip it works, if I try https://nas.mydomain.com it doesn't work BUT if I try https://nas.mydomain.com when I am connected to my mobile network then it works.

Synology says that maybe my router doesn't support the local loopback but that doesn't seem the case. Any idea what I could do?

 

[ColinTaylor]

NAT loopback is working fine as demonstrated by the fact that it works with HTTP.

I suspect the problem is with the way HTTPS validates the source address. It thinks that the data has been "tampered with" because the source address had been changed by the loopback.

 

[eibgrad]

As I read the OP's description, I took http://mynasip to mean he was accessing that from inside the local network. And if that's the case, we don't have proof NAT loopback is working.

 

[ColinTaylor]

As I read the OP's description, I took http://mynasip to mean he was accessing that from inside the local network. And if that's the case, we don't have proof NAT loopback is working.

Oops Good spot. I read that but my brain translated it into http://nas.mydomain.com/ (which is the usual question we get asked here.) That said, NAT loopback on Merlin is a very well worn subject and in itself is known to work (within its normal limitations).

@AlexKalopsia Can you confirm whether or not you can access your NAS via http://nas.mydomain.com/ from within your LAN?

If it doesn't work what error message do you get? Also, what is returned from "nslookup nas.mydomain.com"?

 

[Martineau]

Hi everyone, I am having a problem with the local loopback on my A66U.

I reach my NAS via https://nas.mydomain.com from within my local network. I now realized that if I try and upload some files via http://mynasip it works, if I try https://nas.mydomain.com it doesn't work BUT if I try https://nas.mydomain.com when I am connected to my mobile network then it works.

Synology says that maybe my router doesn't support the local loopback but that doesn't seem the case. Any idea what I could do?

You don't specify which RT-AC66U firmware you are running.

If you are running a release prior to v384.4

384.4 (16-Mar-2018)
   - REMOVED: Merlin NAT loopback mode (was increasingly
              problematic as the firmware firewall handling became
              more complex)

then there is an option in the GUI to choose between ASUS' and RMerlin's NAT loopback method.
If the choice exists, try the alternative.