# Packet Tracer companion lab

The presenter demonstrates on the physical Catalyst and TP-Link switches. You reproduce the same ideas in your
own Packet Tracer network during minutes 36-48, after the concept slides. You do not need to connect your laptop to the demo equipment.
Watching or sharing a screen with another attendee is fine if Packet Tracer is not ready.

## Before the session

1. Download Packet Tracer for your computer from the [Cisco Resource Hub](https://www.netacad.com/resources/lab-downloads).
   Follow [Cisco's installation and first-launch instructions](https://www.netacad.com/skillsforall/files/Cisco_Packet_Tracer_Download_and_Installation_Instructions.pdf).
2. Install it and complete the required Cisco sign-in before arriving. Launch it again to check access.
   Use a supported desktop/laptop OS; Packet Tracer is not a phone/tablet app.
3. Build the starter topology below and save it before sending any traffic. Save a local copy of this guide too.
   Installation and account troubleshooting are outside the one-hour session.

There is no supplied `.pkt` file yet. These instructions describe how to create your own. The Packet Tracer
workflow has not been exercised in the app for this repo; the presenter should rehearse it before distributing
the lab as a tested activity. Menu labels and available commands can differ by release.

## Build your starter network

In a new **Logical** workspace, add two PCs from **End Devices** and one **2960** switch from
**Network Devices > Switches**. The simulated switch does not need to match the physical 3560's exact model.

Connect each PC's `FastEthernet0` to a different switch port with **Copper Straight-Through** cables:

```text
PC0 (host A) --- Switch0 (2960) --- PC1 (host B)
                  Fa0/1  Fa0/2
```

Use PC0 to switch `FastEthernet0/1` and PC1 to switch `FastEthernet0/2`. Wait for the links to forward.
Leave the switch's default access-port/VLAN settings in this new activity.

On each PC, open **Desktop > IP Configuration**, select static IPv4 configuration, and enter:

| Setting | PC0 / host A | PC1 / host B |
| --- | --- | --- |
| IPv4 address | `192.168.50.10` | `192.168.50.20` |
| Subnet mask | `255.255.255.0` | `255.255.255.0` |
| Default gateway | Unset | Unset |
| DNS server | Unset | Unset |

Do not add a router, internet cloud, or DHCP server. Save as `networking-starter.pkt` before your first ping.
During the session, use **Save As** to make a working copy so you can reopen the starter if you get lost.

## Follow the physical demo

| Session time | Presenter: actual equipment | You: Packet Tracer |
| --- | --- | --- |
| 36:00-38:00 | Trace the two hosts and Catalyst connections | Open your starter; check the addresses and links |
| 38:00-42:00 | Ping, inspect ARP and the Catalyst MAC table | Run the commands below; optionally step through ARP/ICMP |
| 42:00-45:00 | Move B behind the TP-Link switch | Watch first; add a second simulated switch if you are ready |
| 45:00-48:00 | Unplug B, reconnect, observe recovery | Disconnect/reconnect B's simulated cable and repeat ping |

The minimum finish is **one successful ping, one peer ARP entry, and one learned switch MAC entry**.
The second switch and packet animation are extensions. Stop when the presenter moves on; this is not a race.

### 1. Ping and compare the tables

On PC0, open **Desktop > Command Prompt**:

```text
ipconfig
ping 192.168.50.20
arp -a
```

Packet Tracer's PC prompt is simulated. Use plain `ping` here; the Windows presenter's `-n` and `-t` options
are not required. An initial timeout can occur while neighbor resolution or link forwarding completes; retry once.

Open Switch0's **CLI** tab, press Enter if necessary, and use:

```text
enable
show mac address-table
```

Expected: A can reach B, A learns a peer IP-to-MAC mapping, and Switch0 learns the hosts' source MACs on their ports.
Compare values from your own activity; they will not match the presenter's hardware MAC addresses.

### 2. Optional: watch ARP before ICMP

Before your first ping, switch to **Simulation** mode and use **Edit Filters** to show **ARP** and **ICMP**.
Use **Add Simple PDU**, select PC0 then PC1, and advance with **Capture / Forward**. Inspect an event's PDU
information to connect Ethernet addressing to the IP/ICMP conversation. Return to **Realtime** before moving cables.

Ask: why does the host need a MAC address before it can send to the local IPv4 peer?
If the peer is already cached, ARP may not appear. Reopen the untouched starter and try before generating traffic.
**Reset Simulation** clears the event list; do not assume it clears every device's learned state.

### 3. Optional: put another switch in the path

Remove only B's original cable in your simulation. Add a second 2960, connect B to it, then connect the switches
with exactly one link, using **Automatically Choose Connection Type** if needed. For example, use `Fa0/24` on
each switch for that inter-switch link. Leave the new switch's access ports in the default VLAN.

Send traffic again and inspect Switch0. B's source MAC should now be learned toward the second switch.
The second 2960 represents the TP-Link's forwarding role, not its exact hardware or management features.
Do not add a second parallel inter-switch link.

### 4. Disconnect and recover

Remove B's cable in your simulation, then try the ping again. Reconnect it and wait for forwarding before retrying.
A table entry may remain after disconnection; cached state does not prove current reachability.
Save your working activity if you want to explore it after the workshop.

## If something goes wrong

- Check both PC addresses, masks, cable endpoints, and link status. Same subnet and same VLAN are required here.
- If you are still stuck after a minute, watch the physical demo or pair with someone. Continue later from your starter.
- Do not change your real laptop's network settings to fix the simulated network.
- A simulated link rate or delay is not a measurement of the actual Catalyst, TP-Link, or travel router.
- The GL.iNet demonstration remains presenter-led. No matching simulated travel router is required.

## References

- [Cisco: first Packet Tracer lab](https://tutorials.ptnetacad.net/help/default/myFirstPTLab.htm)
- [Cisco: Simulation Mode](https://tutorials.ptnetacad.net/help/default/mode_simulation.htm)
- [Cisco: PDU information](https://tutorials.ptnetacad.net/help/default/mode_simulation_PDUinfo.htm)