BitDefender VPN and Synology NAS

Dabares

I have a Synology NAS set up for Time Machine backups, but it seems BitDefender VPN interferes with this setup. Turning on VPN seems to result in the NAS not being available, or failing, when TM tries to access it. SynologyAssistant also cannot find the NAS, when VPN is active. I've tried split tunneling, and a few other things, with no luck. The result is if I want my TM to do a backup, I have to manually remount the NAS if I've used VPN and I must turn off VPN if I want to service the NAS at any level.

From what I've found on your support, BitDefender is not compatible with this configuration, nor is there any plan to address it, in the immediate future.

Is this correct of am I missing a setting?

Alexandru_BD

Hello,

I can think of the following explanation. When the VPN is connected, all network traffic from your computer is routed through the VPN tunnel, including local network traffic. This means your PC no longer sees local IP devices the same way, they appear inaccessible because traffic isn’t going over your LAN interface. Bonjour/mDNS discovery and SMB broadcasts to the NAS are blocked or don’t traverse the VPN tunnel and tools like Synology Assistant or Time Machine can’t find the NAS because LAN broadcasts are not going through the VPN. In other words, this is expected behavior for most consumer VPNs unless they specifically support local LAN passthrough which Bitdefender VPN generally does not do for file shares and NAS devices.
Also, the split tunneling feature lets you route applications outside the VPN tunnel, not arbitrary LAN/IP addresses themselves. It simply won’t work to bypass VPN for local network addresses. It is designed to bypass VPN for internet traffic, not to bridge LAN traffic around the VPN tunnel.

Synology’s official Time Machine troubleshooting documentation even lists disabling or uninstalling third-party security software as a troubleshooting step because such software can interfere with backups. Bitdefender is named among them alongside other AV vendors when network backups fail.

https://kb.synology.com/en-us/DSM/tutorial/Time_Machine_backup_failed?

Regards