openvpn tunnel is slower for select IP addresses

Question

I have a bit of a weird problem with openvpn. I am running an openvpn server on an asus router at home and I have an openvpn client on another router (netgear running dd-wrt) in another location.

My initial setup for the client was to pass all connections through the tunnel, but this was not an idea situation. Then I found that I could add on the client, only specific IPs that I need to use the tunnel and so I did. One IP was for a DVR for security cameras and another IP was for a server for home automation.

The problem I am experiencing is that before when all traffic was going through the tunnel, I could see the cameras (they have an application for android where you can connect and see them) no problem. Now, after I route only the DVR and server traffic (the server is mostly unused at the moment because I haven't started the home automation project yet. It is just running proxmox at the moment), I can see only some of the cameras at a time and quite a bit of a lag.

It appears that the VPN tunnel is much slower now. What could be the problem for this? Is the client router not coping? Is it more taxing to only route traffic for specific ips than for the entire network?

Please keep in mind that I don't have much experience and I may not have chosen the best solution. I am happy to provide more details on request since I don't know what is relevant in this case.

Answer 1

After some more reading it appears (but bare in mind I am no authority on the subject!) that there are some problems with priority based routing in dd-wrt when something called Shortcut Forwarding Engine is enabled. This feature is in the Setup section towards the top.

By disabling this feature (which I do no understand what it does!) policy based routing works great. No I have my two IPs going through the tunnel and the rest of the clients connected to the vpn client router are going through the ISP WAN.