Network Unreachable - Ethernet

Question

I'm trying to get my new Ubuntu Server install connected to the internet, but Im running into an issue. I cant even ping the router that the server is directly plugged into via Ethernet. I've tried looking at a number of forums and setting the OS to use DHCP, setting static IPs, etc. And now I am here. Hoping that someone can point out where my problem lies.

This is a fresh install of Ubuntu Server version 18.04.3

Command outputs (note, typing this on a phone):

$ ifconfig
enp3s0: flags=4163<UP, BROADCAST, RUNNING, MULTICAST> mtu 1500
inet6 <IPv6address1> prefix 64 scopeid 0x0
inet6 <IPv6address2> prefix 64 scopeid 0x20
ether <macHere> ...

point is, ethernet iface is up, but no IPv4 listed. Only other interface is lo.

$ cat /etc/network/interfaces
auto lo
iface lo inet loopback

auto enp3s0
iface enp3s0 inet static #Ive tried dhcp here in place of static, without the following lines

address 192.168.1.101
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1

Router gateway is 192.168.1.1, I've double checked

$ cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 <hostname>

::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

/etc/resolv.conf is managed by systemd-resolved so I would prefer not to manually edit this

$ cat /etc/resolv.conf
nameserver 127.0.0.53 #??? Don't understand why this is
options edns0

$ systemd-resolve --status
...
Link 2 (enp3s0)
  Current Scopes: none
  LLMNR setting: yes
  MulticastDNS setting: no
  DNSSEC setting: no
  DNSSEC supported: no

ip route show and ip route list do not print anything to stdout

Please let me know what I can do to fix this issue. I can edit this post with more output if needed

EDIT: While the potential duplicate question is similar, it does not provide a solution on how to connect to the internet with the tools available on the system (aka netplan). That question is asking how to switch back to etc/network/interfaces, and the currently accepted answer is to apt install ifupdown (which is a brilliant idea considering networking is unavailable).

Answer 1

In Ubuntu 18.04 and later, ifup/down, implemented by /etc/network/interfaces, is replaced by netplan. Therefore, please revert the faulty entries. From the terminal:

sudo nano /etc/network/interfaces

Take out all the entries except:

auto lo
iface lo inet loopback

Save (Ctrl+o followed by Enter) and exit (Ctrl+x) the text editor.

Next, let's clean up your netplan file:

sudo nano /etc/netplan/01-netcfg.yaml

Change the file to read:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp3s0:
      addresses:
        - 192.168.1.101/24
      gateway4: 192.168.1.1
      nameservers:
          addresses: [192.168.1.1, 8.8.8.8]

Netplan is very specific about indentation and spacing. Please proofread carefully twice. Follow with:

sudo netplan generate
sudo netplan apply

After these changes, reboot and let us see:

ip addr show
ping -c3 www.ubuntu.com