On (Arch) Linux, I configured a VPN, which I do not want to use for all the traffic, but for the software that binds to the associated tun/tap interface. So far, with the help of iproute2's policy routing, this is working well.
The VPN has a nameserver, which I want the software, that taps into the VPN, to use. Where do I put that nameserver's address, without ending up having the other software trying to use it? Which is what I get, putting it into