Uploaded November 2025 | Updated September 2026, 3 weeks ago

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Routers need an IPv4 address configured on an interface to enable that interface to route packets that enter or need to exit that interface. The configuration requires little thought: Configure the planned IP address and wildcard mask (in dotted decimal format) at the end of the *ip address* interface subcommand. The difficulties come in planning the addresses, the related IPv4 subnetting math, and troubleshooting various routing problems.

In this Config Lab, plus several others like it, you begin with a set of routers that do not yet have IPv4 addresses configured. Your job: Do the math and follow the lab instructions to choose the IPv4 addresses to use for each router interface. Then configure those addresses and confirm that they work.

📘 Matches CCNA Official Cert Guide:
*Volume 1 Chapter 17 Section 2*

*Chapters*
00:00 Introduction
01:09 Topology and Initial State
01:58 Lab Instructions
02:51 Extra Lab Instructions (Connected Routes and ARP)
03:51 Extra Details for CML-Free

*Config Lab Blog Page:*
CLAB203: IPv4 Addresses 3
👩🏼‍💻 certskills.com/clab203

*The Related Config Lab Review Video:*
📽️ youtu.be/GvhYNdL2SEA

*The Related Instructional Video about Connected Subnets*
📽️ youtu.be/ZciZ4N_boxY


*📽️ Lab Tools and Labs Playlist:* youtube.com/playlist?list=PLhDAmDsTz9XfxFJCydqlcjvO4gT6xTPgj


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*Product Links*
Product links below. I make a small affiliate sales commission if you buy something!

CCNA Library (Two Book Set):
📚 ccna.link/nu-cp-lib-ed2

All CCNA products at Cisco Press:
🖨️ ccna.link/nu-cp-allccna

All Wendell's products at Cisco Press:
🧔🏼‍♂️ ccna.link/nu-cp-allwo

Ciscopress.com/NewCerts Page (News, Announcements):
📰 ccna.link/nu-cp-newcerts
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