So it's an odd issue. Got some "file" servers, basically Synology/Netgear NAS boxes which users connect to whilst in the office, and remotely especially in the last few months.
The last Synology I added recently (Synology FS1018, let's call it SYN3), it was all configured, all good, working internally just as you'd expect it to, but for some reason, cannot ping it or access it over IPSEC VPN! The other Synology's are fine (SYN1 and SYN2), along with other servers.
Nothing special with rules etc, the IPSEC VPN is configured to access everything on the Local LAN, which the servers are part of, but just this one server is the problem. I looked at the SYN3, there is no firewall or any security settings causing any block within the Synology OS itself, it can be accessed just fine internally, and the VPN subnet is an extension of the local LAN, albeit a different IP range.
From the firewall, I can ping SYN3 just fine, using either DNS or it's IP, but not from the VPN clients!
Any ideas why I cannot communicate this particular server that may spring to mind?
It's the FG100E, on 6.2.3 firmware.
I am lucky in the sense that the users connect to their PC's via remote desktop once on the VPN, they can then access the servers, including the problematic one just fine, but if they tried to map a network drive to this particular Synology from their own personal PC's at home, which they may need to access a file quickly, it fails.