Objetivo: mudar para endereços IP estáticos se você usa Debian como um servidor.
[1] O nome da interface [enp1s0] é diferente em cada ambiente, substitua-o pelo seu próprio.
[2] Desative o IPv6 se não precisar dele.
root@debian:~# echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf
root@debian:~# sysctl -p
net.ipv6.conf.all.disable_ipv6 = 1
root@debian:~# ip addr
1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: enp1s0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:0c:48:f6 brd ff:ff:ff:ff:ff:ff
inet 192.168.15.100/24 brd 192.168.15.255 scope global enp1s0
valid_lft forever preferred_lft forever
root@debian:~# vi /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# A interface loopback
auto lo
iface lo inet loopback
# A interface primária
allow-hotplug enp1s0
# comente ou remova a linha a seguir
#iface enp1s0 inet dhcp
# adicione as informações estáticas
iface enp1s0 inet static
address 192.168.15.20
network 192.168.15.0
netmask 255.255.255.0
broadcast 192.168.15.255
gateway 192.168.15.1
dns-nameservers 8.8.8.8
root@debian:~# systemctl restart ifup@enp1s0
root@debian:~# ip addr
1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp1s0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:0c:48:f6 brd ff:ff:ff:ff:ff:ff
inet 192.168.15.20/24 brd 192.168.15.255 scope global enp1s0
valid_lft forever preferred_lft forever
inet6 fe80::5054:ff:fe0c:48f6/64 scope link
valid_lft forever preferred_lft forever