Version: Sep 29, 2025

Setting a Static IP Address on Ubuntu Server

1. Identify Network Interface Details

Use the command:
```
ip addr
```
Identify the network interface name (e.g., eth0, ens33, wlan0) and current IP configuration.

2. Access Netplan Configuration

Ubuntu uses Netplan for network configuration. Locate the configuration file, typically in /etc/netplan/. Common filenames are 01-netcfg.yaml or 50-cloud-init.yaml.
Use:
```
ls /etc/netplan/
```

3. Back Up the Original Configuration

Always back up the file before making changes:

sudo cp /etc/netplan/01-netcfg.yaml /etc/netplan/01-netcfg.yaml.bak

4. Edit the Configuration File

Open the configuration file with a text editor:
```
sudo nano /etc/netplan/01-netcfg.yaml
```

Replace or add the following configuration, substituting with your desired IP, gateway, and DNS:

network:
  version: 2
  ethernets:
    eth0:                   # Replace with your interface name
      dhcp4: false
      addresses:
        - 192.168.1.100/24   # Replace with your desired IP and subnet mask
      routes:
        - to: default
          via: 192.168.1.1   # Replace with your gateway
      nameservers:
        addresses:
          - 8.8.8.8          # Google DNS
          - 8.8.4.4

    eth1:
      dhcp4: false
      addresses:
      - 10.10.10.1/24       # second NIC, this example is a private network

5. Apply Configuration

Apply the changes using:

sudo netplan generate
sudo netplan apply

6. Verify Configuration

Confirm the changes using:
```
ip addr
```
Test connectivity by pinging the gateway or an external IP:
```
ping 8.8.8.8
```

7. Troubleshooting

If the network does not come up after applying the changes:
- Revert to the backup file:
```
sudo cp /etc/netplan/01-netcfg.yaml.bak /etc/netplan/01-netcfg.yaml
sudo netplan apply
```
- Check Netplan syntax before applying changes:
```
sudo netplan try
```
- Verify the correct interface name and ensure no conflicting DHCP settings.

8. Restart Network Services

If issues persist, restart the network service:
```
sudo systemctl restart systemd-networkd
```

9. Optional: Enable forwarding

When you enable IP forwarding, Linux begins routing traffic between interfaces (e.g., from your 192.168.1.0/24 network to your 10.10.10.0/24 network). This is required if Node 1 is acting as a gateway or bridge between your LAN and your direct private network link.
For example, lets say node 1 is your webserver, and node 2 is a NAS, and you decide to private and direct connect node 1 and node 2 together. This private connection is 10.10.10.0 and your other network your workstation is on 192.168.1.0. How to get access 10.10.10.0? We can use node 1 to forward packets instead of an all out gateway, but your workstation needs to know this.

On node 1

echo "net.ipv4.ip_forward=1" | sudo tee -a /etc/sysctl.conf
sudo sysctl -p

On MacOS workstation - temporary

node 1 ip address example is 192.168.1.50

sudo route -n add 10.10.10.0/24 192.168.1.50

On MacOS workstation - permanent

Create a file

sudo nano /Library/LaunchDaemons/com.local.staticroutes.plist

Add:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
  "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key><string>com.local.staticroutes</string>
    <key>ProgramArguments</key>
    <array>
      <string>/sbin/route</string>
      <string>-n</string>
      <string>add</string>
      <string>10.10.10.0/24</string>
      <string>192.168.2.50</string>
    </array>
    <key>RunAtLoad</key><true/>
  </dict>
</plist>

Then load it:

sudo launchctl load /Library/LaunchDaemons/com.local.staticroutes.plist

Now it’ll reapply at every boot.

Test it

You should be able to ping the private network, assuming we made node 1 second NIC 10.10.10.1 and node 2 10.10.10.2

ping 10.10.10.2