How to set default gateway in Ubuntu Server 18.04 with netplan

I have a single network interface on this server named enp2s0 This interface had a static address 192.168.2.xxx with gateway 192.168.2.1 Now I changed the static address in yaml file to 192.168.1.xxx and the gateway too in 192.168.1.1 but every time I restart the server the default gateway comes back to 192.168.2.1 I tried to launch route commmand to remove default gateway and set the new one but if I restart the server it comes back to 192.168.2.1

This is the yaml config file # This file describes the network interfaces available on your system
# For more information, see netplan(5).
network: version: 2 renderer: networkd ethernets: enp2s0: addresses: [192.168.1.10/24] gateway4: 192.168.1.1 nameservers: addresses: [1.1.1.1,1.0.0.1]

Output of networkctl status enp2s0 after reboot

 2: enp2s0 Link File: /lib/systemd/network/99-default.link Network File: /run/systemd/network/10-netplan-enp2s0.network Type: ether State: routable (configured) Path: pci-0000:02:00.0 Driver: r8169 Vendor: Realtek Semiconductor Co., Ltd. Model: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (M4A HW Address: 48:5b:39:02:41:c9 (ASUSTek COMPUTER INC.) Address: 192.168.1.10 192.168.2.100 fe80::4a5b:39ff:fe02:41c9 Gateway: 192.168.2.1 DNS: 1.1.1.1 1.0.0.1

Output of route command after reboot

Tabella di routing IP del kernel
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.2.1 0.0.0.0 UG 202 0 0 enp2s0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 enp2s0
192.168.2.0 0.0.0.0 255.255.255.0 U 202 0 0 enp2s0

Result of networkctl status enp2s0 after restored default gateway to 192.168.1.1

 2: enp2s0 Link File: /lib/systemd/network/99-default.link Network File: /run/systemd/network/10-netplan-enp2s0.network Type: ether State: routable (configured) Path: pci-0000:02:00.0 Driver: r8169 Vendor: Realtek Semiconductor Co., Ltd. Model: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (M4A HW Address: 48:5b:39:02:41:c9 (ASUSTek COMPUTER INC.) Address: 192.168.1.10 fe80::4a5b:39ff:fe02:41c9 Gateway: 192.168.1.1 DNS: 1.1.1.1 1.0.0.1

Output of route command after restored default gateway to 192.168.1.1

Tabella di routing IP del kernel
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.1.1 0.0.0.0 UG 0 0 0 enp2s0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 enp2s0

This is the output of netplan --debug apply command

 ** (generate:4965): DEBUG: 16:17:35.743: Processing input file /etc/netplan/01-netcfg.yaml..
** (generate:4965): DEBUG: 16:17:35.744: starting new processing pass
** (generate:4965): DEBUG: 16:17:35.744: Processing input file /etc/netplan/lo.yaml..
** (generate:4965): DEBUG: 16:17:35.744: starting new processing pass
** (generate:4965): DEBUG: 16:17:35.744: enp2s0: setting default backend to 1
** (generate:4965): DEBUG: 16:17:35.744: Configuration is valid
** (generate:4965): DEBUG: 16:17:35.744: lo: setting default backend to 1
** (generate:4965): DEBUG: 16:17:35.744: Configuration is valid
** (generate:4965): DEBUG: 16:17:35.744: Generating output files..
** (generate:4965): DEBUG: 16:17:35.744: NetworkManager: definition enp2s0 is not for us (backend 1)
** (generate:4965): DEBUG: 16:17:35.744: NetworkManager: definition lo is not for us (backend 1)
DEBUG:netplan generated networkd configuration changed, restarting networkd
DEBUG:no netplan generated NM configuration exists
DEBUG:enp2s0 not found in {}
DEBUG:lo not found in {'enp2s0': {'addresses': ['192.168.1.10/24'], 'gateway4': '192.168.1.1', 'nameservers': {'addresses': ['1.1.1.1', '1.0.0.1']}}}
DEBUG:Merged config:
network: bonds: {} bridges: {} ethernets: enp2s0: addresses: - 192.168.1.10/24 gateway4: 192.168.1.1 nameservers: addresses: - 1.1.1.1 - 1.0.0.1 lo: addresses: - 127.0.0.1/8 vlans: {} wifis: {}
DEBUG:device lo operstate is unknown, not changing
DEBUG:device enp2s0 operstate is up, not changing
DEBUG:{}
DEBUG:netplan triggering .link rules for lo
DEBUG:netplan triggering .link rules for enp2s0

@heynnema

root@ubuntu:~# cat /etc/network/interfaces
# ifupdown has been replaced by netplan(5) on this system. See
# /etc/netplan for current configuration.
# To re-enable ifupdown on this system, you can run:
# sudo apt install ifupdown
root@ubuntu:~# cat /etc/netplan/*.yaml
# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network: version: 2 renderer: networkd ethernets: enp2s0: addresses: [192.168.1.10/24] gateway4: 192.168.1.1 nameservers: addresses: [1.1.1.1,1.0.0.1]
network: ethernets: lo: addresses: ['127.0.0.1/8']

How to solve ?

1 Answer

Change your /etc/network/interfaces to...

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

Remove /etc/netplan/lo.yaml.

Change your /etc/netplan/01-netcfg.yaml file... and be aware of the specific indentation, and assure no tabs...

from:

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network: version: 2 renderer: networkd ethernets: enp2s0: addresses: [192.168.1.10/24] gateway4: 192.168.1.1 nameservers: addresses: [1.1.1.1,1.0.0.1]
network: ethernets: lo: addresses: ['127.0.0.1/8']

to:

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network: version: 2 renderer: networkd ethernets: enp2s0: addresses: [192.168.1.10/24] gateway4: 192.168.1.1 nameservers: addresses: [1.1.1.1, 1.0.0.1]

sudo netplan --debug generate # generate config files

sudo netplan apply # apply new config

reboot # mandatory reboot