Windows client:
C:\>netsh interface ip show dnsservers
Configuration for interface "Local Area Connection"
Statically Configured DNS Servers: 10.0.0.4
Register with which suffix: Primary only
Configuration for interface "Loopback Pseudo-Interface 1"
Statically Configured DNS Servers: None
Register with which suffix: None
EDIT: And for IPv6:
C:\>netsh interface ipv6 show dnsservers
Configuration for interface "Loopback Pseudo-Interface 1"
Statically Configured DNS Servers: fec0:0:0:ffff::1%1
fec0:0:0:ffff::2%1
fec0:0:0:ffff::3%1
Register with which suffix: Primary only
MacOS client:
$ scutil --dns
DNS configuration
resolver #1
search domain[0] : dehakkelaar.nl
nameserver[0] : 10.0.0.4
if_index : 4 (en0)
flags : Request A records
reach : 0x00020002 (Reachable,Directly Reachable Address)
Linux client with dhcpcd5 network manager (Raspbian distro):
$ dhcpcd --dumplease eth0
[..]
domain_name_servers='10.0.0.1'
[..]
Linux client with "NetworkManager":
$ nmcli
[..]
DNS configuration:
servers: 10.0.0.2
domains: dehakkelaar.nl
interface: wlan0
And there are other network managers available for Linux distros that each have their own syntax.