Step-By-Step Ubuntu Server Network Configuration Tutorial

Ubuntu Server Network Configuration

To configure network interfaces and IP addresses on an Ubuntu server, you typically use the netplan tool, which is the default network configuration utility starting from Ubuntu 17.10 (Artful Aardvark) and later versions. Here’s a basic guide on how to do it:

• Find your network interface names: Run the following command to list all network interfaces available on your Ubuntu Server system:

    ip addr show
  

This will show you a list of network interfaces such as eth0, eth1, enp0s3, etc.

• you can also use ifconfig command

    ifconfig
  

root@sanchit:~# ifconfig
ens18: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.23.25.159  netmask 255.255.254.0  broadcast 10.23.25.255
        inet6 fe80::be24:11ff:fede:41ac  prefixlen 64  scopeid 0x20<link>
        ether bc:24:11:de:41:ac  txqueuelen 1000  (Ethernet)
        RX packets 4259937  bytes 826213829 (826.2 MB)
        RX errors 0  dropped 353184  overruns 0  frame 0
        TX packets 24848  bytes 2323464 (2.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ens23: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 20.5.2.206  netmask 255.255.255.0  broadcast 20.5.2.255
        inet6 fe80::be24:11ff:fed2:9451  prefixlen 64  scopeid 0x20<link>
        ether bc:24:11:d2:94:51  txqueuelen 1000  (Ethernet)
        RX packets 1117352  bytes 73356276 (73.3 MB)
        RX errors 0  dropped 214934  overruns 0  frame 0
        TX packets 522570  bytes 32143330 (32.1 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 848  bytes 108345 (108.3 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 848  bytes 108345 (108.3 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

root@sanchit:~# 

• Edit Netplan Configuration File: Netplan uses YAML configuration files located in /etc/netplan/. The main configuration file is typically named something like 01-netcfg.yaml or 00-installer-config.yaml under Ubuntu Server.

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

Or

    sudo nano /etc/netplan/00-installer-config.yaml
  

               00-installer-config.yaml                                                       
# This is the network config written by 'subiquity'
network:
  ethernets:
    ens18:               >> You can change the interface type as per your conifguration, i:e eth or ens.
      dhcp4: false       >> DHCP disbled if you want to enable DHCP replace false with True and save config.
      addresses:         >> to defien the IP address. 
       - 10.23.25.159/23
      routes:            >> you can add multiple routes
       - to: 0.0.0.0/0
         via: 10.23.24.1
      nameservers:       >> DNS servers
       addresses: [8.8.8.8]
    ens23:               >> you can add multiple interfaces as per your requirement. 
      addresses:
       - 20.5.2.206/24
  version: 2

• Configure the interfaces and IP addresses: Inside the YAML file, you define your network interfaces and their corresponding IP addresses. Here’s a basic example of how it might look in Ubuntu Server:

network:
  ethernets:
    ens18:
      dhcp4: false
      addresses:
       - 10.23.25.159/23
      routes:
       - to: 0.0.0.0/0
         via: 10.23.24.1
      nameservers:
       addresses: [8.8.8.8,8.8.4.4]
    ens23:
      addresses:
       - 20.5.2.206/24
  version: 2                                         
 metric: 100

In this example:

• ens18 is the name of the interface.
• dhcp4: false disables DHCP and assigns a static IP address.
• addresses: [10.23.25.159/23] sets the static IP address and subnet mask.
• nameservers: addresses: [8.8.8.8, 8.8.4.4] sets the DNS servers.
• routes section is added to define additional routes.
• – to specifies the destination network in CIDR notation.
• via specifies the gateway for the route.
• metric is an optional parameter to set the priority of the route. Lower values indicate higher priority.
• Adjust the values according to your network configuration.

• Apply the configuration: After you’ve made your changes, save the file and apply the configuration using the following command:

    sudo netplan apply
  

• Verify the configuration: You can verify that the configuration has been applied correctly by checking the network settings in Ubuntu Server:

    ip addr
  

 root@sanchit:/etc/netplan# ip add
1: lo: <LOOPBACK,UP,LOWER_UP> 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: ens18: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether bc:24:11:de:41:ac brd ff:ff:ff:ff:ff:ff
    altname enp0s18
    inet 10.23.25.159/23 brd 10.23.25.255 scope global ens18
       valid_lft forever preferred_lft forever
    inet6 fe80::be24:11ff:fede:41ac/64 scope link 
       valid_lft forever preferred_lft forever
3: ens19: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether bc:24:11:01:a2:26 brd ff:ff:ff:ff:ff:ff
    altname enp0s19
4: ens20: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether bc:24:11:e3:8d:3b brd ff:ff:ff:ff:ff:ff
    altname enp0s20
5: ens21: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether bc:24:11:83:4f:ad brd ff:ff:ff:ff:ff:ff
    altname enp0s21
6: ens22: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether bc:24:11:7a:73:01 brd ff:ff:ff:ff:ff:ff
    altname enp0s22
7: ens23: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether bc:24:11:d2:94:51 brd ff:ff:ff:ff:ff:ff
    altname enp0s23
    inet 20.5.2.206/24 brd 20.5.2.255 scope global ens23
       valid_lft forever preferred_lft forever
    inet6 fe80::be24:11ff:fed2:9451/64 scope link 
       valid_lft forever preferred_lft forever

These commands will display the current network configuration including IP addresses in Ubuntu Server.

• Use “ip route show” command to check the Routes

    ip route show
  

root@sanchit:/etc/netplan# ip route show
default via 10.23.24.1 dev ens18 proto static 
10.23.24.0/23 dev ens18 proto kernel scope link src 10.23.25.159 
20.5.2.0/24 dev ens23 proto kernel scope link src 20.5.2.206 

• To add temporary Route in Ubuntu Server(it will remove after system or service restart )

    sudo ip route add 10.10.0.0/16 via 192.168.1.1 dev ens33
  

Restart networking service (if necessary): Sometimes, especially on older Ubuntu Server versions, you might need to restart the networking service for changes to take effect. You can do this with:

    sudo systemctl restart networking
  

That’s it! Your Ubuntu Server should now be configured with the specified network interface and IP address.

Useful Links

https://ubuntu.com/server

https://sanchitgurukul.com/basic-networking

https://sanchitgurukul.com/network-security