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 foo.bar, which is a DNS server, followed by multiple subdomains x.foo.bar, 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: ~foo.bar
Testing queries only for x.foo.bar 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 . : foo.bar
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.
