# Exercise 1 — Subnetting Math by Hand

## Scenario

You've been given the block `10.20.0.0/22` for a small office and asked to carve it into subnets before any equipment is racked.

## Deliverables

1. **Base facts.** State the total number of addresses in `10.20.0.0/22`, and how many usable host addresses that is if it were left as a single subnet (show the arithmetic, per theory section 5).

2. **Even four-way split.** Subnet `10.20.0.0/22` into exactly 4 equal-sized subnets. For each of the 4, state: the CIDR block, the network address, the first usable host, the last usable host, and the broadcast address.

3. **Uneven split.** Instead, the office actually needs: a 100-device "workstations" subnet, a 20-device "servers" subnet, and a 6-device "management" subnet. Choose the smallest CIDR prefix for each that has enough *usable* host addresses (not just total addresses), and lay all three out as non-overlapping blocks within the original `10.20.0.0/22`, in the order given. Show the CIDR, network address, and usable range for each.

4. **Gateway placement.** For the "workstations" subnet from part 3, state which address you'd conventionally assign as the default gateway and why that convention exists (per theory section 6).

## Notes

- Show your work as binary or arithmetic, not just final answers — the goal is the subnetting math itself, not just the right numbers.
- Addresses only need to be internally consistent with your own carving, not tied to any real-world allocation.