[solved] Weird issue with TailScale on Synology devices

asheenlevrai · April 24

Hello everyone

Foreword:

I consider myself a fairly "advanced" user (I learned over the years) but I'm not deeply familiar with technicalities related to either networking nor backup/synchronization or whatever. I have no training in informatics. I'm mostly "self" taught thanks to the many of you on the internet who patiently and kindly shared their knowledge and expertise (and I am very thankful to each of you). For many around me, I'm the person people go to when they have an issue with their computer. Imposter Syndrome for sure...

I started using Synology years ago since I was comfortable with DSM and its GUI. I'm not super comfortable with CLI although I use it occasionally (usually when I have no other option, pardon my weakness).

I'm not super familiar with TailScale. I don't fully understand how it works. for instance, I don't know what "Tailnet", "route" or "exit node" mean but it seemed to me like this was not necessary for what I was trying to achieve.

Question:

I experience a weird issue when trying to use TailScale between Synology devices. First let me explain the details of the setup.

I have 5 Synology NASes, 4 at home and 1 at work. Let's identify them with letters:

A) is my main NAS at home. It hosts all my files
B) is my secondary NAS at home. It hosts mostly media files that I could re-download in case of an unrecoverable loss
C) is my backup NAS at home. It hosts backup of A) and some of the content of B)
D) is a smaller spare NAS at home. I use it mostly for tests/experiments
E) is my backup NAS at work. It hosts backups of A) and some of the content of B), or at least it's what it is supposed to.

I setup all the backup tasks using Synology Hyper Backup. all my NASes run DSM7 (7.1 or 7.2) and the current version of TailScale.

The NAS at work is behind a firewall (or other network security solutions) that I have zero control over. At some point I could no longer connect from the outside in an easy way (we no longer had "public IPs" AFAIU).

Therefore I started to use TailScale to be able to backup A) and some of the content of B) onto E). I installed TailScale on A), B) and E) and they all appear as connected on my TailScale admin console. I also installed TailScale on my laptop so that I can connect to DSM on E) and manage it from home.

I setup weekly backups (A) + B) -> E) ) and everything worked fine for 5 weeks. After that A) could no longer reach E) although B) still could. Weird...

In order to troubleshoot this (is the issue coming from A)?) I decided to install TailScale on C) and D) and see if they could reach E). They couldn't. Both C) and D) do appear as connected on TailScale's admin console.

B) has no problem performing backup on E) thanks to TailScale, and this has been going on for over a year now. I don't understand why A) (C) or D) ) cannot do the same though.

My laptop at home has no problem connecting to E) over HTTPS thanks to TailScale.

I don't know how I could figure out the origin of the problem.

I'd be very thankful if you would share any advice with me. Considering my limitations I will probably have to Google parts of your replies in order to figure out what you mean.

(I understand that some would rather recommend to completely move away from Synology and use CLI based tools or different OSes. I'm not sure I feel ready for that ATM. I'm not familiar with Docker containers either.)

Thank you very much in advance for your help.

Best,

-a-