UDM Pro L2TP VPN - Synology NAS as client - L2TP connection failing

VPN
1

Hi!

I just got my UDM Pro (yesterday) and have set everything (apart from the VPN) up. Everything is working great, I just can’t get the L2TP VPN to work. Teleport works fine from my iPhone, not sure if this is relevant though.

I have one Synology NAS at my place, another Synology NAS at my parents’ place for off-site backup.
I set up a VPN to be able to sync the contents of the two.

I was previously (up until yesterday) running an ASUS RT-AC86U on which an OpenVPN VPN server was configured. The Synology NAS at my parents’ place connected just fine to my router and sync worked flawlessly.

They have the same ISP as they’ve had before. I have the same ISP as I had when I had my previous router, so no changes there.

My UDM Pro subnet is 192.168.1.0/24, the VPN Advanced Configuration is on Auto but shows 192.168.3.0/24 (although greyed out). The network at my parents’ place is 192.168.2.0/24.
So… there shouldn’t be any conflicts there as far as I am aware.

I have

  • Rebooted my UDM Pro
  • Double checked my DDNS, the IP is correct
  • Double checked credentials + pre-shared key, no typos (everything is copy + pasted)
  • Googled a bunch without becoming much wiser
  • Run out of ideas…

The error on the Synology NAS is “L2TP connection failed. Please check your profile settings and try again.”

Any troubleshooting tips?

Thanks in advance!

2

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3

I had the same issue, had to enable “Use default gateway on remote network” to connect to UDM.

4

Thanks for the answer. I gave up in the end and installed OpenVPN server on the NAS.

L2TP VPN works for other things but never got it to work properly for the NAS.