Find the block size
The mask's last relevant octet is 192.
256 − 192 = 64
Each subnet block jumps by 64 in the last octet.YOUR CCNA LEARNING SPACE
Networking, made click.
Small lessons. Visual explanations. One idea at a time. Learn it, watch it, then try it yourself.
🧩 One concept at a time👀 See how it works🧠 Recall it with practice
YOUR LEARNING PATH
A little progress adds up.
Start with the first concept. Mark each lesson complete as you go.
0 of 4
Progress is kept for this visit only.
THE BIG PICTURE
Think of a network like a delivery service.
Devices are the places, IP addresses are the destinations, switches help deliver locally, and routers choose the road to another network.
Your laptopCreates data
Ethernet / Wi-Fi
SwitchLocal delivery
IP network
RouterChooses a route
Next hop
ServerReceives request
Watch the little packet travel. The real network moves bits; the animation is a mental model.
LESSON 1 · NETWORK DEVICES
Each device has a job.
Tap a device to focus on its role. Keep this simple distinction in mind while troubleshooting.
🔀
MOSTLY LAYER 2
Switch = local delivery
A Layer 2 switch learns MAC addresses and forwards Ethernet frames toward the correct local port.
Remember it: Switches connect things in the same local network.
Try in a lab: show mac address-table dynamic
LESSON 2 · TROUBLESHOOTING
The OSI model is a troubleshooting map.
You don't need to memorize a paragraph for every layer. Learn the order, then connect each layer to a symptom.
L3
FOCUS ON THIS
Network
IP addressing and routing move packets between networks.
Example symptom
You can reach your local gateway, but a remote subnet is unreachable.
Useful check: show ip route
Memory ladder: All People Seem To Need Data Processing.Application · Presentation · Session · Transport · Network · Data Link · Physical (layers 7 → 1)
LESSON 3 · SUBNETTING
Subnetting is sorting addresses into blocks.
Follow the steps in order. Don't try to solve everything in your head at once.
Let's solve 192.168.10.70/26 together.
Find the block your IP belongs to
Block starts: 0, 64, 128, 192. The IP ends in 70, so it falls in the 64–127 block.
0–6364–127 ← your IP128–191192–255
Read the answers
Network = first address. Broadcast = last address. For traditional subnets, usable hosts are between them.
Network192.168.10.64
Broadcast192.168.10.127
Usable range192.168.10.65 – 192.168.10.126
Usable hosts62
Step 1 of 3
Quick mental model: prefix → block size → find the matching block → network and broadcast → usable range. The calculator is a checker, not a substitute for practicing the steps.
LESSON 4 · SWITCHING
A VLAN is a separate neighborhood.
Access ports put an endpoint in one VLAN. Trunks carry traffic for multiple VLANs between network devices.
VLAN 10 · STAFF💻🖨️Separate broadcast domain
VLAN 20 · GUEST📱💻Separate broadcast domain
SwitchAccess ports assign a VLAN
Devices in different VLANs need Layer 3 routing to communicate. A VLAN alone is not a firewall.
Show a Cisco IOS access-port example
configure terminal
vlan 20
name GUEST
exit
interface GigabitEthernet1/0/10
description Guest endpoint
switchport mode access
switchport access vlan 20
spanning-tree portfast
no shutdown
end
show vlan briefUse PortFast only on edge ports connected to end devices. Confirm interface naming and VLAN policy before applying configuration.
LOW-PRESSURE PRACTICE
Can you recall it without looking?
Try from memory first. Getting an answer wrong is useful feedback, not failure.
POCKET REFERENCE
Commands worth knowing
Learn what each command answers, not just how it looks.
show ip interface briefWhich Layer 3 interfaces are up, and what IPs do they have?show interfaces statusWhich switch ports are connected, and what VLAN/speed do they show?show vlan briefWhich VLANs exist, and which access ports belong to them?show interfaces trunkWhich trunks are active, and which VLANs are allowed?show mac address-table dynamicWhich MAC addresses has the switch learned?show ip routeWhere would this router forward a packet?show loggingWhat events has the device recorded?