Danke für die schnelle Antwort. Ich habe aus Sicherheitsgründen den richtigen Output auf die Beispieldomain servername.de resp. auf die IP's 115.16.12.0/24 umgeschrieben.
root@server1:~# cat /etc/resolv.conf
nameserver 127.0.0.1
nameserver 115.16.12.1
nameserver 1.1.1.1
root@server1:~# cat /etc/nsswitch.conf
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.
passwd: compat
group: compat
shadow: compat
gshadow: files
hosts: files dns
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis
root@server1:~# host servername.de
servername.de has address 115.16.12.11
servername.de has IPv6 address 2c0d:1f7:d1:1500::e6
servername.de mail is handled by 30 server40.servername.de.
servername.de mail is handled by 10 server35.servername.de.
servername.de mail is handled by 15 server12.servername.de.
root@server1:~# host server1.servername.de
server1.servername.de has address 115.16.12.20
root@server1:~# host server1.servername.de 1.1.1.1
Using domain server:
Name: 1.1.1.1
Address: 1.1.1.1#53
Aliases:
server1.servername.de has address 115.16.12.20
root@server1:~# cat /etc/hosts
127.0.0.1 server1.servername.de server1 server1.servername.de server1 localhost
115.16.12.20 server1.servername.de server1