Uploaded March 2025 | Updated September 2026, 2 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 itself requires little thought: Just configure the planning 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.

*Config Lab Blog Page:*
CLAB117: IPv4 Addresses 2
👩🏼‍💻 certskills.com/clab117

*The Related Config Lab Review Video:*
📽️ TBD

*The Related Instructional Video: Calculate Subnets*
📽️ youtu.be/BOQQbfDShGU


*Chapters*
00:00 Introduction
01:09 Topology and Initial State
02:10 Lab Instructions
03:19 Extra Details for CML-Free
04:05 Testing from CML Hosts (Router-as-Many-Hosts)


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

*Extra Detail about CML-Free*

📽️ The CML-Free Five-Node Workaround (Discusses Background about Router-as-Many-Hosts): youtu.be/8LAmPxqa1Go

📽️ How to Use the CML-Free Router-as-Many-Hosts Workaround: youtu.be/oHqV9tvT2-g

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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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