How to direct all traffic in OpenVPN to DD-WRT and exclude some from there?

Question

linux

Good afternoon.
The task is as follows:
There is a router with DD-WRT. The OpenVPN Client is deployed there.
Now if the VPN is disconnected, all traffic goes directly.
How to implement the following?
- when VPN is disabled, traffic is cut (kill switch);
- 1 IP address forward directly without VPN. Since the router is a rather weak thing, the VPN from it is extremely slow (it is used for devices on which VPN cannot be enabled). And where you can turn it on - it connects directly from the device. Accordingly, this VPN IP must be added to the exceptions and sent directly if it is connected to from any devices.
A big request to paint in detail for iptables, I'm not special in these matters, so it will be quite difficult to understand the explanations in words.
Thank you.

Answer 1

Details - in any guide on setting up routing for VPN. Otherwise, this is not a question, but a task.
In general, you make separate routes for addresses of interest not through a VPN. Because they propagate to smaller subnets, they will take precedence over the default gateway or whatever your traffic is routed into the tunnel.