Tim:
Are you on-line?
And did any of the other options work?
ToddAndMargo:
No. And I am also not running sysyemd-resolved
Perhaps we should go back to the start, your question is itself a bit
odd. DNS means Domain Name System, but we all presume you want to
know
the address of your Domain Name Server.
When a device joins a network it is typical that a DHCP server assigns
it an addresses (numerical IP, hostname, domain name), and provides
some other addresses (gateway IP, nameserver(s), subnet mask). The
DHCP server need properly configuring to provide that info. Your
device will glean that info, and use it, even if you are running your
own name server.
And one would expect that all of that gets cancelled when
disconnecting
(not that people often cleanly disconnect, as opposed to just losing
connection).
Failing that, without a DHCP server, variously named auto-config
schemes can take place (Bonjour, ZeroConf, etc) which do a similar
task. This time, the device, itself, self sets several of those
parameters, but not in a way that can communicate outside of the
network. It'll pick a random IP address from within a local-only
range, it'll broadcast hostname queries waiting for an answer from
anyone.
Failing that, you hand set your network configuration.
Normally, when you connect up to your ISP their DHCP server assigns
you
all that networking info. Some don't, some expect you to set some
things, though that's an older way of doing things. And some just
fail
badly. If you want to know your ISP's DNS servers to put into your
network configuration, or into your name daemon's forwarder IPs, you
could try:
a) Connecting via DHCP and copying the details
b) Asking them what the DNS server IPs are
c) Googling them
Bearing in mind that an ISP's DNS servers may change, at any time,
they
may expect you to use DHCP to keep them current.
If there's a router between your ISP and your device, *it* will have
your ISP's DNS IPs in it, as your ISP's DHCP server will have
configured it, and you can copy them. And *it* will probably act as
your DHCP server for the rest of your network. You may be able to
customise its DHCP settings to suit your LAN. That router will act as
your DNS server, or simply pass queries through. You can use that
router's IP as your DNS forwarder IP.
You may not need to use your ISP's DNS servers, you could simply use
Goggle's, or some other public DNS server (there are various public
ones, with and without censoring). This may actually be better for
you
than your ISP's. The only gotcha is that some ISPs will give a
different answer to their mailserver's IP to their own clients than to
the rest of the world.
