TUTORIAL
How to Configure an IP Address on a Cisco Router
by Jon Welling
Project Overview
EXPERIENCE LEVEL: Intermediate
TIME TO COMPLETE: 30-45 minutes
ESTIMATED COST: Free (assuming you already have a Cisco router or lab emulator)
Skills Needed
Basic knowledge of Cisco IOS commands
Understanding of IP addressing and subnet masks
Familiarity with OSI model layers 1 and 2
Before You Begin
Before you start configuring, keep these things in mind:
Enterprise-grade routers ship with all interfaces administratively down by default. You’ll need to enable them before traffic can flow.
Know the IP address your router should use. This usually comes from your ISP or network documentation.
Remember: misconfiguring a router can “black hole” traffic, effectively dropping data instead of forwarding it. That’s why verifying settings before plugging it into a live network is essential.
Tools and Materials Needed
A Cisco router (physical or virtual)
Console cable or emulator access (like Cisco Packet Tracer or GNS3)
Terminal software (e.g., PuTTY or Tera Term)
Assigned static IP address and subnet mask (or DHCP if your ISP provides it)
How to Configure an IP Address on a Cisco Router
Routers, unlike switches, aren’t plug-and-play. Cisco switches can often be connected to a network and start working almost immediately. Routers, however, need to be assigned an IP address and activated before they can pass traffic. If you skip this step, your router won’t know where to send data, causing outages instead of connectivity. So how do you do that?
Watch the video walkthrough below, or keep reading for a step-by-step guide:
Step 1: Verify the Current Interface Configuration
Most Cisco routers usually ship with all interfaces shut down by default. If you skip this check, you might assign an IP address to an interface that’s either disabled or physically disconnected.
Connect to the router and enter privileged exec mode: enable
Display all interfaces: show ip interface brief
This output shows:
Interface names (e.g., GigabitEthernet0/0)
IP addresses (if any are already assigned)
Status (Layer 1: physical connection)
Protocol (Layer 2: link state)
Status messages to know:
Up: Interface is physically connected and working
Administratively Down: Disabled by configuration (default)
Down: No signal (often unplugged cable or faulty hardware)
If you don’t understand the difference between Status and Protocol, troubleshooting becomes guesswork. Status is about whether the hardware/cable is good (Layer 1), while Protocol confirms whether the interface is receiving valid signals (Layer 2).
Step 2: Choose the Interface to Configure
After confirming the state of all interfaces, pick the one you’ll assign the IP address to. Be careful to match the console designation with the physical port so you don’t plug into the wrong interface later.
Enter global configuration mode: configure terminal
Select the interface: interface gigabitethernet0/0
Tip: Use ? after interface to see a list of available ports.
Choosing the right interface is more than guesswork—plugging into the wrong one could mean your router doesn’t talk to the rest of your network at all.
Step 3: Assign an IP Address
Routers are the “traffic directors” of a network. If they don’t know where to forward packets, data gets sent into purgatory and simply dropped. Assigning an IP address ensures the router knows where it belongs in the network. Now, let's set the IP address and subnet mask.
In interface configuration mode, assign the IP address: ip address 192.168.1.1 255.255.255.0. Then replace it with the IP and subnet from your ISP or internal documentation.
If your ISP uses DHCP instead of static IP, use this: ip address dhcp
Then, verify the change: show ip interface brief
Where does that IP come from? For businesses, the static IP usually comes from your ISP. Static addressing ensures consistency for VPNs, DNS entries, or hosted services. Smaller businesses may use DHCP, which works but isn’t reliable for services that depend on a fixed external address.
Step 4: Enable the Interface
Assigning the IP address isn’t enough. By default, router interfaces are administratively down, so you need to enable them.
Confirm with: show run. This shows the current configuration, including whether the interface is down.
Select the interface again if needed: interface gigabitethernet0/0
Bring it online: no shutdown
You should see console messages showing that the interface is now “up” at both Status (Layer 1) and Protocol (Layer 2). On physical devices, the port lights should blink.
Until you enable the interface, your router is essentially offline. This step flips the switch from “hardware installed” to “network active.”
Wrapping Up
That’s it—you’ve just configured a Cisco router with an IP address. Quick recap:
Check the interface status using this command: show ip interface brief
Enter config mode with configure terminal
Select the interface with interface <name>
Assign an IP address (or DHCP) with ip address
Enable the interface with no shutdown
Keep practicing until this feels natural—it’s a foundational skill for any network administrator.
Want to learn more about subnetting, routing, and securing routers? Take our CCNA Training Course or browse other Cisco tutorials.