Computer Science · 12th Grade

Active learning ideas

Routing and Switching

Active learning works for routing and switching because these concepts are abstract and spatial. When students manipulate virtual devices, build subnets, and compare address types, they turn theory into tangible experience. This hands-on approach clarifies how traffic moves through networks and reduces confusion between local and global forwarding decisions.

• Common Core State Standards
• CSTA: 3B-NI-03
• CCSS.ELA-LITERACY.RST.11-12.3

• 20–50 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Simulation Game
• 40 min · Whole Class

Simulation Game: Router Decision Tables

Give each student a routing table card listing two or three destination networks and which port leads to them. Students arrange themselves as nodes in a simple network drawn on the whiteboard. The teacher sends a message to a specific IP address, and the class routes the message hop by hop, each router consulting their card to decide where to forward it next.

What happens when a critical node in a global network fails and how is traffic rerouted?

Facilitation Tip

For the Router Decision Tables activity, assign each group a different subnet mask so their tables look distinct, making it easier to spot patterns during the debrief.

What to look for

Present students with a diagram of a small network including two routers and several end devices. Ask them to identify which device is a router and which is a switch, and to label the IP address and subnet mask for two devices on different networks.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 02

• Inquiry Circle
• 50 min · Small Groups

Inquiry Circle: Subnetting Challenge

Groups receive a scenario: a school district needs to divide one Class C network block into subnets for five departments of different sizes. They calculate subnet masks, determine valid host ranges, and verify their work does not leave address conflicts. Groups present their design and explain the trade-offs they made between subnet size and number.

Differentiate between the functions of routers and switches in a network.

Facilitation Tip

In the Subnetting Challenge, provide colored cards or markers so students can visually separate subnets on their whiteboards before writing the final configuration.

What to look for

Pose the scenario: 'Imagine a major internet exchange point in a large city experiences a power outage, rendering its core routers offline. How would traffic destined for continents across the ocean be rerouted, and what technologies enable this resilience?' Facilitate a class discussion on redundancy and dynamic routing protocols.

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Activity 03

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: IPv4 vs. IPv6

Present the fact that IPv4 supports about 4.3 billion addresses , a number that seemed impossibly large in the 1980s but became exhausted in the 2010s. Students individually brainstorm what caused the shortage, then pair up to compare ideas and share with the class. The discussion leads naturally into how IPv6's 128-bit addressing solves the problem.

Design a simple network topology and explain how data would be routed between devices.

Facilitation Tip

During the IPv4 vs. IPv6 discussion, assign roles like 'IPv4 defender' or 'IPv6 advocate' to push students into defending their positions with evidence.

What to look for

Provide students with a simple IP address (e.g., 192.168.1.50) and a subnet mask (e.g., 255.255.255.0). Ask them to calculate the network address and determine if another device with IP address 192.168.1.100 is on the same subnet.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

A few notes on teaching this unit

Teach routing and switching by starting with the physical building metaphor. Use analogies like mail rooms for switches and postal services for routers to ground abstract addressing in familiar systems. Avoid overwhelming students with binary math early. Instead, let them experience address calculation through guided steps before introducing formulas. Research shows that students grasp subnet masks better when they see how changing one octet directly alters host capacity.

By the end of these activities, students will confidently explain the difference between switches and routers using MAC and IP addressing. They will calculate subnets based on real-world host requirements and justify IPv4 vs. IPv6 decisions with technical reasoning. Look for accurate labeling on diagrams and precise calculations in their work.

---

Watch Out for These Misconceptions

• During Simulation: Router Decision Tables, watch for students who group all devices under one forwarding table, assuming routers and switches operate identically.

  Use the router decision tables to show that switches use MAC tables to forward frames within a single network, while routers consult IP tables to forward packets between different networks. Ask students to physically separate their tables into 'Local Delivery' and 'Remote Routing' sections.

• During Collaborative Investigation: Subnetting Challenge, watch for students who assume all subnets must be equal in size.

  Direct students to the unequal subnetting scenario in the challenge materials. Have them calculate host capacity for subnets sized 126 and 14 addresses and compare the subnet masks. Ask them to explain why the mask 255.255.255.128 allows 126 hosts but 255.255.255.240 only allows 14.

---

Methods used in this brief

• Simulation Game
• Inquiry Circle
• Think-Pair-Share