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 โ observe how MAC addresses change at R1 while IPs stay constant |
| 6 | Inspect ARP tables โ see that PC1 has R1's MAC, not PC2's MAC |
| 7 | Knowledge check โ 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 โ 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 โ 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 โ 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 ๐ฆ Packet Trace in the top bar to step through exactly what happens to the frame headers at each hop.
Use Tab to complete commands ยท โ โ for history ยท Switch devices using the toolbar above the terminal.