Objectives
| # | Objective |
|---|
| 1 | Configure IP address and default gateway on PC1 |
| 2 | Configure IP address and default gateway on PC2 |
| 3 | Configure both interfaces on R1 and verify routing table |
| 4 | Ping from PC1 to PC2 across the routed boundary |
| 5 | Open Packet Trace — observe how MAC addresses change at R1 while IPs stay constant |
| 6 | Inspect ARP tables — see that PC1 has R1's MAC, not PC2's MAC |
| 7 | Knowledge check — encapsulation and de-encapsulation concepts |
Key Concepts
| Concept | What it means |
|---|
| Encapsulation | Wrapping data in headers at each layer as it travels down the OSI stack. Each layer adds its own addressing and control information. |
| De-encapsulation | Stripping headers at each layer as the packet travels up the stack at the destination — the reverse of encapsulation. |
| MAC addresses hop-by-hop | Ethernet MAC addresses only carry traffic between adjacent Layer 2 devices. The router re-encapsulates with new MACs at every hop. |
| IP addresses end-to-end | Source and destination IP addresses in the IP packet header never change across a routed network — only the MAC addresses do. |
| Default gateway | The IP address of the router interface on the same subnet as the host. Used for traffic destined to a different subnet. |
Supported Commands
| Device | Command | Purpose |
|---|
| PC1 / PC2 | ip <addr> <mask> <gw> | Set IP address and default gateway |
| PC1 / PC2 | show ip | Show IP and gateway configuration |
| PC1 / PC2 | ping <ip> | Test connectivity |
| PC1 / PC2 | show arp | Show ARP table — notice gateway MAC |
| R1 | enable | Enter privileged EXEC mode |
| R1 | configure terminal | Enter global configuration mode |
| R1 | interface <name> | Enter interface configuration |
| R1 | ip address <addr> <mask> | Assign IP to router interface |
| R1 | no shutdown | Bring the interface up |
| R1 | show ip interface brief | Verify all interface IPs and state |
| R1 | show ip route | Verify routing table has both subnets |
Once the ping works, click 📦 Packet Trace in the top bar to step through exactly what happens to the frame headers at each hop.
Use Tab to complete commands · ↑ ↓ for history · Switch devices using the toolbar above the terminal.