# IPv4 Subnetting Evidence Lab

**Time:** 45 minutes

**Level:** Introductory networking / CCNA preparation
**SciFunLab guide:** https://scifunlab.com/topics/ip-subnetting

## Learning objective

Derive the network address, broadcast address, usable range, and host capacity from an IPv4 address and CIDR prefix, then verify the reasoning with the visual subnetting lab.

## Before the lab

Without a calculator, predict the network and broadcast addresses for `192.168.10.77/26`. Write the block size or binary boundary used in your reasoning.

## Investigation

1. Open the IP Subnetting topic guide and launch the subnetting lab.
2. Test `192.168.10.77/26` and record the calculated network, broadcast, first host, last host, and host capacity.
3. Repeat for `/24`, `/27`, and `/30`, keeping the IPv4 address fixed.
4. For each prefix, explain which bits identify the network and which remain for hosts.

| Prefix | Network | Broadcast | First host | Last host | Usable hosts |
|---|---|---|---|---|---:|
| /24 | | | | | |
| /26 | | | | | |
| /27 | | | | | |
| /30 | | | | | |

## Explain the evidence

- What happens to host capacity each time one more bit is added to the prefix?
- Why are the network and broadcast addresses normally excluded from usable host addresses?
- Which prefix in the table is suitable for a point-to-point exercise requiring two usable IPv4 addresses?
- How can you tell whether two addresses belong to the same subnet?

## Extension

Design two non-overlapping subnets inside `10.20.0.0/24`: one for at least 50 hosts and one for at least 20 hosts. State each CIDR block and verify it in the lab.

## Assessment evidence

Collect the prediction, completed table, VLSM extension, and topic knowledge-check result. Require written boundary reasoning rather than calculator output alone.