Noob - issue with Synology hyper backup

Hi :slight_smile:

I’m kinda new to Tailscale and, a few months ago, I set it up on 2 Synology NAS at home (DS1819+ and DS1821+) so that they can perform weekly backups to a Synology NAS at work (DS918). The NAS at work is behind a closed LAN and requires VPN to connect to, hence Tailscale… I also set up Tailscale on 2 additional NASes at home (DS414 and DS214play).

Now, for a few weeks, everything went well and offsite backups occurred without any issue. All of a sudden, one of the NAS at home (DS1821+) could no longer reach the NAS at work (DS918), while the 2nd NAS at home (DS1819+) never experienced any issue and still continues to perform its weekly backup as usual.

At first I thought this could be due by an incompatibility between Tailscale and the latest version of DSM since the DS1821+ was recently upgraded to DSM7.1.1 Update 3 while the DS1819+ was running DSM7.1.1 Update 1 (update 3 was not even offered as an update). FWIW, the DS918 is still running some earlier version of DSM7.0.1.

However, this is not the case since I noticed the following:

  • the recent upgrade to all my NASes to DSM7.1.1 Update 4 didn’t fix the problem for the DS1821+ and didn’t cause the issue to appear on the DS1819+ either.
  • 2 other NASes at home (DS414 and DS214play) also run Tailscale but can neither reach the NAS at work (DS918).

I also know the problem is not coming from the DS1821+ since it can perform backups on the DS414 using Tailscale IP without any issue. And, again, neither the 414 nor the 214play can reach the 918 for some reason…

All NASes seem to be properly connected according to what I can see in Tailscale admin console.

I’m probably missing something here but I hope some of you can share their knowledge and wisdom :slight_smile:

Thank you very much in advance for your help.

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