Configuring Network Connections with nmcli

1. From Automatic to Manual: DHCP vs. Static IP

Most computers on a home or office network get their IP address automatically from the router. This process is called DHCP (Dynamic Host Configuration Protocol). It's convenient because it requires no configuration, but the IP address can change, for example, after a reboot.

For a server—even a local development server—this isn't ideal. We need a predictable address. This is where a static IP comes in. You manually assign a permanent IP address, gateway, and DNS server to the machine.

To do this, you'll need to know:

• IP Address: The new, static address you want to assign.
• Subnet Mask/Prefix: Defines the size of your local network (e.g., 255.255.255.0 or /24).
• Gateway: The IP address of your router, which connects your local network to the internet.
• DNS Server: The server that translates domain names (like google.com) into IP addresses.

2. Modifying a Connection with nmcli

In the last lesson, you used nmcli connection show to view connection details. Today, we'll use its counterpart: nmcli connection modify.

The following guide provides a concise, step-by-step breakdown of the commands needed to set a static IP. It's an excellent reference for the process we're about to undertake.

As you saw in the article, the process involves modifying several properties of the connection profile one by one. While you can issue separate commands for each property, nmcli also allows you to set them all in a single command for efficiency.

Let's watch a video demonstration from Red Hat that shows how to switch a connection from auto (DHCP) to manual (static) and apply the IP address and gateway settings in one step.

3. Do-It-Yourself: Set a Static IP on Your System

Now it's time to put this into practice on your own Fedora machine. We will walk through the entire process, from gathering information to verifying the final result.

Warning: Executing these commands will temporarily disconnect your network. This is normal. Since you are working on your local machine, you won't be locked out.

Step 1: Plan Your Configuration

Before making changes, you need to know what to change.

1. Find your active connection name. You'll need this for all subsequent commands.

   nmcli connection show --active
   

   Note the name in the NAME column. Let's assume it's "Wired connection 1".

2. Gather your current network details. Your static configuration should be similar to your current one.

   nmcli connection show "Wired connection 1"
   

   Look for these lines and write down the values:

   • ipv4.method: Should be auto.
   • IP4.ADDRESS[1]: Your current IP and prefix (e.g., 192.168.1.15/24).
   • IP4.GATEWAY: Your router's IP (e.g., 192.168.1.1).
   • IP4.DNS[1]: Your current DNS server.

3. Choose a new Static IP. You must pick an address that is on the same network but is not likely to be assigned to another device by DHCP. A safe bet is to pick an address with a high last number.

   • For example, if your current IP is 192.168.1.15, a good choice for a static IP would be 192.168.1.200.

Step 2: Apply the Static Configuration

Now, use nmcli to modify your connection. Remember to use sudo because these are system-wide changes. Replace "Wired connection 1" with your actual connection name and use the IP addresses you just gathered and chose.

# Set the static IP address and subnet prefix
sudo nmcli connection modify "Wired connection 1" ipv4.addresses 192.168.1.200/24




# Set the gateway (your router's IP)
sudo nmcli connection modify "Wired connection 1" ipv4.gateway 192.168.1.1




# Set the DNS servers (we'll use Google's and Cloudflare's public DNS)
sudo nmcli connection modify "Wired connection 1" ipv4.dns "8.8.8.8 1.1.1.1"




# IMPORTANT: Switch the method from DHCP to manual
sudo nmcli connection modify "Wired connection 1" ipv4.method manual

This screenshot illustrates a similar process.

Step 3: Activate and Verify

Your changes are saved but not yet active. Apply them by reactivating the connection.

# This command re-applies the configuration. Your connection will drop and reconnect.
sudo nmcli connection up "Wired connection 1"

Now, verify everything:

1. Check your IP address. The inet field should show your new static IP.

   ip a
   

2. Test connectivity to your gateway.

   ping -c 3 192.168.1.1
   

3. Test internet connectivity.

   ping -c 3 8.8.8.8
   

If all pings are successful, congratulations! You've successfully configured a static IP.

Step 4: How to Revert to DHCP

Knowing how to undo a change is just as important. Switching back to DHCP is simple.

# Set the method back to auto
sudo nmcli connection modify "Wired connection 1" ipv4.method auto




# It's good practice to clear the manual settings you added
sudo nmcli connection modify "Wired connection 1" ipv4.addresses ""
sudo nmcli connection modify "Wired connection 1" ipv4.gateway ""
sudo nmcli connection modify "Wired connection 1" ipv4.dns ""




# Re-activate the connection to get a new IP from your router
sudo nmcli connection up "Wired connection 1"




# Verify you're back on an automatic IP
ip a

For now, feel free to switch back to DHCP. You can re-apply the static configuration whenever you start a development session.

Conclusion

In this lesson, you took a significant step in managing your Fedora system's network. You've gone from simply reading information to actively configuring it.

Key Takeaways:

• Static IPs provide a stable, predictable network address, which is crucial for any kind of server.
• The primary command for changing network settings is nmcli connection modify.
• You must configure four main properties for a basic static IPv4 setup: ipv4.method, ipv4.addresses, ipv4.gateway, and ipv4.dns.
• Changes are applied by reactivating the connection with nmcli connection up <name>.

You now have a solid foundation for network configuration. In the next lesson, we will explore tools like ping and traceroute in more detail to test network reachability and diagnose connectivity problems.