Configuring Network Settings in Ubuntu Server: Basics and Troubleshooting

Introduction to Network Configuration on Ubuntu Server

Configuring network settings for a server is essential for successful operation. This article covers basic network configuration using Netplan and troubleshooting steps to resolve common networking issues.

Basic Network Configuration

1. Checking your interface information

Use the following command to check the status of available network interfaces:

1user@machine:~$ ip addr

In our example output it shows two network interfaces, the system loopback lo and our enp0s3 interface.

 11: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
 2    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
 3    inet 127.0.0.1/8 scope host lo
 4       valid_lft forever preferred_lft forever
 5    inet6 ::1/128 scope host noprefixroute 
 6       valid_lft forever preferred_lft forever
 72: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
 8    link/ether 00:1b:21:00:00:00 brd ff:ff:ff:ff:ff:ff
 9    inet 192.168.1.10/24 brd 192.168.1.255 scope global dynamic noprefixroute enp0s3
10       valid_lft 6077sec preferred_lft 6077sec
11    inet6 fe80::1c68:8197:5a52:f1b2/64 scope link noprefixroute 
12       valid_lft forever preferred_lft forever

2. Finding your Netplan Configuration

Your Netplan configuration will be located in the /etc/netplan/ directory. The filename may differ, however this can be checked using the following command:

1user@machine:~$ ls /etc/netplan/

When you have found it, open it in your favourite text editor but remember to use sudo as this file will need root privileges.

1user@machine:~$ sudo nano /etc/netplan/01-netcfg.yaml

3. Examples of a Netplan Configuration

Here is an example that configures DHCP for IPv4 on the enp0s3 network interface.

1network:
2  version: 2
3  renderer: networkd
4  ethernets:
5    enp0s3:
6      dhcp4: true

Here is an example that configures a static IPv4 address, subnet, default route, and two DNS servers on the enp0s3 network interface.

 1network:
 2  version: 2
 3  renderer: networkd
 4  ethernets:
 5    enp0s3:
 6      dhcp4: false
 7      addresses:
 8        - 192.168.1.100/24
 9      routes:
10        - to: default
11          via: 192.168.1.1
12      nameservers:
13        addresses:
14          - 8.8.8.8
15          - 8.8.4.4

4. Apply the changes

To apply the changes without rebooting just run the following:

1user@machine:~$ sudo netplan apply

If the configuration does not work as intended you can get more information with the following:

1user@machine:~$ sudo netplan --debug apply

Troubleshooting Networking Issues

1. Checking Network Connectivity

To verify network connectivity you can use the ping command. If the following is successful, it indicates that your system is able to connect out:

1user@machine:~$ ping 8.8.8.8

However if the next command is successful, it indicates that your system is able to connect out as well as being able to resolve DNS queries.

1user@machine:~$ ping google.com

Conclusion

Configuring network settings in Ubuntu Server is essential for connectivity and accessing resources on a network. By following these basic configuration steps and troubleshooting techniques outlined in this article, you can effectively set up and troubleshoot basic network connections on your Ubuntu Server system.