@MR.S I like the idea of an IPSec (non-L2TP) tunnel. I haven't used these before but it seems the server supports them so if the ER605 does too then this could be a good thing to try to see whether...

@Clive_A The server has fixed IP but the client doesn't. I may be wrong but my understanding was that for L2TP with IPSec the server needed to validate the client's IP. Maybe a DNS name is enough and...

@d0ugmac1 Thanks for raising some questions to help me provide more useful background. The server is a DrayTek Vigor 2925, the client a TP-Link ER605. The server is at the static IP address...

@Clive_A did you see the message saying that the ER605 does not have a static IP address? How would you use L2TP without a static IP address?

@d0ugmac1 I'm using PPTP because the ER605 end does not have a static IP address. When you say bounce, do you mean just briefly disconnect? Have you tried leaving the server offline for an extended...

If the VPN server is not available when the router restarts and then subsequently comes online the ER605 does not seem to attempt to connect to it once it comes online. This is using a LAN-to-LAN...