OpenVPN and dhcp-option domain-route for Windows/Linux

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I am trying to understand the dhcp-options usage for Windows and Linux (Ubuntu).

There seems to be difference between the implementation.

Using OpenVPN 2.4 server and client, i test on Windows 10 21H2 and Ubuntu 20.04. I have a domain, which is a DNS server, followed by multiple subdomains, which are with private IPs and not public DNS records.

The options that are of interest to me are:

dhcp-option DOMAIN and dhcp-option DOMAIN-ROUTE

I first found some forum post, that if i want to route specific DNS requests for X domain only, i should use DOMAIN-ROUTE.

And so i did set a push option on the OpenVPN server. On Ubuntu, using resolvectl status, i get the DNS Domain: Testing queries only for returns expected results. So it works.

But when i tried it under Windows i observed the following error: Options error: --dhcp-option: unknown option type 'DOMAIN-ROUTE' or missing or unknown parameter

After searching for a bit, i was surprised, that i could not find any information about DOMAIN-ROUTE.

Looking at the IANA BOOTCP DHCP Parameters, i could not find such option there.

Then i went and used the DOMAIN option when testing for both Windows and Ubuntu. This time, i could see it on Windows as well: Connection-specific DNS Suffix . : But DNS queries did not work, since it keeps trying to use the default DNS server, instead of the pushed one.

Question is:

what is DOMAIN-ROUTE and how it differs from DOMAIN?

Is there an dhcp-option, that would work the same way on Windows, as it does on Linux, in regards to querying a specific DNS server when the requested DNS matches a domain search list/suffix.

I sit in a Tesla and translated this thread with Ai:


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