As the configuration of the hosts is identical I assumed that. But it’s a good idea to check resolv.conf. Both have:
**erlangen:~ #** ll /etc/resolv.conf
lrwxrwxrwx 1 root root 32 Nov 25 20:56 /etc/resolv.conf -> /run/systemd/resolve/resolv.conf
**erlangen:~ #** cat /etc/resolv.conf
# This is /run/systemd/resolve/resolv.conf managed by man:systemd-resolved(8).
# Do not edit.
#
# This file might be symlinked as /etc/resolv.conf. If you're looking at
# /etc/resolv.conf and seeing this text, you have followed the symlink.
#
# This is a dynamic resolv.conf file for connecting local clients directly to
# all known uplink DNS servers. This file lists all configured search domains.
#
# Third party programs should typically not access this file directly, but only
# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
# different way, replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.
nameserver 192.168.178.1
nameserver fd00::xxxx:xxxx:xxxx:xxxx
search fritz.box
**erlangen:~ #**
I even powered off host erlangen and removed it from the 7490, but to no avail:
**erlangen:~ #** journalctl -b -u systemd-networkd -u systemd-resolved.service --no-pager
Nov 27 06:47:04 erlangen systemd[1]: Starting Network Configuration...
Nov 27 06:47:04 erlangen systemd-networkd[657]: lo: Link UP
Nov 27 06:47:04 erlangen systemd-networkd[657]: lo: Gained carrier
Nov 27 06:47:04 erlangen systemd-networkd[657]: Enumeration completed
Nov 27 06:47:04 erlangen systemd[1]: Started Network Configuration.
Nov 27 06:47:05 erlangen systemd-networkd[657]: eth0: Interface name change detected, renamed to enp42s0.
Nov 27 06:47:05 erlangen systemd-networkd[657]: enp42s0: Configuring with /etc/systemd/network/wired.network.
Nov 27 06:47:05 erlangen systemd-networkd[657]: enp42s0: Link UP
Nov 27 06:47:06 erlangen systemd[1]: Starting Network Name Resolution...
Nov 27 06:47:06 erlangen systemd-resolved[909]: Positive Trust Anchors:
Nov 27 06:47:06 erlangen systemd-resolved[909]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d
Nov 27 06:47:06 erlangen systemd-resolved[909]: Negative trust anchors: home.arpa 10.in-addr.arpa 16.172.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa 168.192.in-addr.arpa d.f.ip6.arpa corp home internal intranet lan local private test
Nov 27 06:47:06 erlangen systemd-resolved[909]: Using system hostname 'erlangen'.
Nov 27 06:47:06 erlangen systemd[1]: Started Network Name Resolution.
Nov 27 06:47:08 erlangen systemd-networkd[657]: enp42s0: Gained carrier
Nov 27 06:47:10 erlangen systemd-networkd[657]: enp42s0: Gained IPv6LL
Nov 27 06:47:12 erlangen systemd-networkd[657]: enp42s0: DHCPv4 address 192.168.178.20/24, gateway 192.168.178.1 acquired from 192.168.178.1
**erlangen:~ #**
**erlangen:~ #** tracepath -4 erlangen
1: erlangen.fritz.box 0.037ms reached
Resume: pmtu 65535 hops 1 back 1
**erlangen:~ #** tracepath -6 erlangen
tracepath: erlangen: No address associated with hostname
**erlangen:~ #**