The Opener
Last issue I promised you an answer on real gear versus Packet Tracer. This one’s a little personal, because real gear is how I ended up here.
Last week I posted about the dusty box that got me into networking. I was a business education teacher. One day in our school’s computer lab, I noticed five little eight-port Netgear boxes daisy-chained together, covered in dust, with a red light that wouldn’t stop blinking. The light said “collision.” I had no idea what that meant, so I Googled the model number and that one word.
They were hubs. A hub repeats everything out every port, so when two computers talk at the same instant, the signals run into each other and you get garbage. Every forum post said the same thing: get switches. So I walked into my principal’s office and said, “We need to buy switches.”
I didn’t plan a career change that day. A red light made me curious, and I kept pulling the thread.
So, the question a viewer asked: do you need physical equipment to learn this? Short answer, no. The longer answer is below.
The Deep Dive: What I’d actually buy, and when I wouldn’t buy anything
My dusty-box story makes it sound like you need hardware to get hooked. You don’t. You need something you’re allowed to break. Here’s how I’d do it if I were starting today.
Start with Packet Tracer. It’s free.
Cisco Packet Tracer is free with a Cisco Networking Academy account, and it covers most of what the CCNA tests: VLANs, trunks, spanning tree, OSPF, ACLs, NAT, DHCP.
Its best feature is something real gear can’t do. Flip it into Simulation mode and you can step through traffic one packet at a time, then click into any packet and see what’s inside it, layer by layer. You can watch a frame leave a PC and see exactly which ports a hub or a switch sends it out of. On real gear, you get a blinking light.
The limits are real, though. It’s a simulator, so it imitates Cisco’s software instead of running it. Most CCNA commands work, some don’t, and some output is simplified. And you never touch a cable.
The free middle step: CML-Free
When you want real Cisco software without spending money, Cisco Modeling Labs has a free version. It runs actual Cisco images, up to five devices at a time, as a virtual machine on your computer. That’s enough for two switches, a router, and a couple of hosts. You’ll want a computer with some RAM to spare.
When real gear is worth it
You’ve worked through most of the CCNA material in a simulator and want the physical side: console cables, slow boot times, a cable that isn’t seated, password recovery.
You’re interviewing for a job where you’ll touch hardware, and you want to stop being nervous around it.
You learn better with something blinking in front of you. That’s a legit reason. It was mine.
What I’d actually buy
Two used Cisco Catalyst 2960-X switches, so you can build a real trunk between them. They’re going for about $50 to $90 each on eBay right now.
One used Cisco ISR 4321 router, around $80.
A USB console cable, about $20.
That’s roughly $200 to $280 for a kit that covers the CCNA. If it’s going in your bedroom, look at the 8-port 2960-CX instead. It costs a little more, but it has no fan, so it’s silent.
When I wouldn’t buy anything
You haven’t finished the basics in Packet Tracer yet. A switch won’t teach you subnetting.
You want it because someone online has a rack. You saw mine come out of a closet. You don’t need one.
It’s a 48-port PoE monster. Those are cheap for a reason: loud, hot, and hungry for power.
It’s a prebuilt “CCNA lab kit” that costs more than buying the same pieces yourself.
Whichever route you pick, my free Home Lab Starter Guide has starter diagrams to build from.
The takeaway: tonight, open Packet Tracer. Build two switches with a trunk between them, put PCs in three VLANs, and get them pinging. Then type the command from this week’s Reader Question, the one without add, and watch what breaks. Then fix it. That costs nothing, and nobody has to drive to a site.
The Week in Networking
Arista’s VeloCloud Orchestrator, the system that manages a VeloCloud SD-WAN, had a critical flaw that let a low-level user give themselves operator rights. It was already being exploited. Arista patched its hosted version. On-prem customers have to update themselves.
Why it matters: Attackers go after whatever controls everything else. And running it yourself means the patching job is yours too.
Thousands of Spectrum customers lost internet and phone service after storms damaged aerial fiber. The first restoration estimate came and went, and customers didn’t get a new one until the next afternoon.
Why it matters: The physical layer still breaks the most stuff, and no simulator models a storm. And when it’s down, keeping people updated is part of the job.
New episode of my podcast with Alexis Bertholf. Girard is a network and security engineer raising seven kids, and we get into how he handles burnout.
Why it matters: If you’re studying at night after a full shift somewhere else, burnout is the thing most likely to stop you. Not the material.
Reader Question
“I didn’t understand the commands. Are they really dangerous?”
From a YouTube comment on my Halloween video, lightly edited.
Yes. That one is genuinely scary.
A trunk is a link that carries several VLANs between switches. That trunk was carrying VLANs 120, 130, and 140, and I wanted to add 110. So I typed:
switchport trunk allowed vlan 110
That doesn’t add 110 to the list. It replaces the whole list with just 110. The second I hit Enter, everything on 120, 130, and 140 stopped crossing that link. The switch doesn’t ask if you’re sure. If your management traffic was on one of those VLANs, your remote session dies too, and now someone is driving to the site with a console cable.
The command I meant was:
switchport trunk allowed vlan add 110
One missing word. @brightspark263 called it in the comments before I could reply.
Three habits that keep this from happening to you:
Look before you touch. Run
show interfaces trunkand copy the allowed list before you change anything. Run it again after, and compare.Use
addandremove. Only type a full list when you mean to replace the whole thing.Give yourself an undo on remote changes. Before a risky change on a device you can’t walk up to, run
reload in 10. If you lock yourself out, the switch reboots in 10 minutes back to its saved config. If everything works, runreload cancel, then save. Don’t save before you’ve checked, or the reboot brings back the broken version. The reboot is a short outage, but it’s a lot shorter than the drive.
The Close
Next week: is networking headed where software engineering is? A viewer asked if this field is as bleak as software jobs feel right now. I’ll tell you what I’m actually seeing from the inside.
If you build that trunk lab and something breaks that you can’t explain, bring it to The Network Node, my free Discord. Still no course, still nothing to sell.
Short versions all week on YouTube, TikTok, Instagram, and LinkedIn. Got a question for next week’s Reader Question? Hit reply.
The Weekly Packet by Kevin Nanns
Enterprise network architect. Content creator. adjacentnode.com