Lab Overview
This lab develops hands-on IP addressing and subnetting skills. You will manually calculate subnet ranges using VLSM (Variable Length Subnet Masking), assign addresses to router interfaces and hosts, apply configurations in Cisco IOS, and verify end-to-end connectivity.
Complete all calculation tables with pencil/paper first before touching any device. Router configurations must match your planned address scheme exactly — verify with
show ip interface brief before testing pings.
Subnetting Quick Reference
| Prefix | Mask | Hosts |
|---|---|---|
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
| Formula | Calculation |
|---|---|
| Usable Hosts | 2ⁿ − 2 |
| Subnets from Block | 2ˢ |
| Network Address | IP AND mask |
| Broadcast Address | last addr in block |
| Next Subnet | NW + block size |
Task 1: Binary Conversion Practice
Converting between decimal and binary is the core skill underlying all subnetting. Complete the table below without a calculator. Use the bit-value row (128·64·32·16·8·4·2·1) as your reference.
Write out 128·64·32·16·8·4·2·1 above each blank. Subtract from the decimal value greedily — if the bit value fits, place a 1; otherwise place a 0.
Task 2: Fixed-Length Subnetting (FLSM)
Scenario: Your organisation is assigned the network block 192.168.10.0/24. You need to divide it into 8 equal subnets. Complete the entire subnet table below.
| Subnet # | Network Address | Subnet Mask / CIDR | First Usable Host | Last Usable Host | Broadcast |
|---|---|---|---|---|---|
| 1 | 192.168.10.0 | /27 | |||
| 2 | /27 | ||||
| 3 | /27 | ||||
| 4 | /27 | ||||
| 5 | /27 | ||||
| 6 | /27 | ||||
| 7 | /27 | ||||
| 8 | /27 |
Task 3: VLSM Design
Scenario: You are allocated 172.16.0.0/16. Design a VLSM scheme for a company with the following departments. Always subnet largest requirement first.
| # | Department | Hosts Needed | CIDR / Mask | Network Address | Usable Range | Broadcast |
|---|---|---|---|---|---|---|
| 1 | Engineering | 500 | ||||
| 2 | Sales | 200 | ||||
| 3 | Marketing | 100 | ||||
| 4 | HR | 50 | ||||
| 5 | Management | 20 | ||||
| 6 | WAN Link A | 2 | ||||
| 7 | WAN Link B | 2 |
Task 4: IOS Interface Configuration
PC-A PC-B
192.168.10.x 172.16.0.x
| |
Fa0/0 [R1] Gi0/0 ---- Gi0/0 [R2] Fa0/0
.1/27 .1/23
WAN /30 link
Apply the addresses from your VLSM plan to R1. Substitute the correct prefix lengths from your calculations in Task 3.
R1# configure terminal R1(config)# interface FastEthernet0/0 R1(config-if)# ip address 172.16.0.1 255.255.254.0 ! ← your value R1(config-if)# no shutdown R1(config-if)# description Engineering-LAN R1(config-if)# exit
R1(config)# interface GigabitEthernet0/0 R1(config-if)# ip address 172.16.X.Y 255.255.255.252 ! ← your value R1(config-if)# no shutdown R1(config-if)# description WAN-to-R2 R1(config-if)# end
R1# show ip interface brief R1# show ip route R1# ping 172.16.X.Y ! ping R2 WAN address R1# ping 172.16.2.1 ! ping R2 LAN gateway
Check that static or dynamic routing is configured between R1 and R2. A directly connected link alone does not install routes to remote subnets. Add a static route or configure OSPF/EIGRP as directed by your instructor.
Task 5: Identify Address Classes & Types
For each IP address below, identify the class (A/B/C/D/E), state whether it is public or private (RFC 1918), and note if it is a valid host, network, or broadcast address in the given prefix.
| IP Address | Given Prefix | Class | Public / Private | Host / NW / Broadcast |
|---|---|---|---|---|
| 10.0.0.255 | /24 | |||
| 172.31.255.255 | /16 | |||
| 192.168.1.1 | /24 | |||
| 8.8.8.8 | /24 | |||
| 224.0.0.5 | N/A | |||
| 169.254.0.5 | /16 |
Review Questions
| Q1 |
A host is assigned 192.168.5.130/26. What is the network address, broadcast address, and valid host range for its subnet? |
| Q2 |
Why must VLSM subnets always be allocated in order from largest to smallest? What goes wrong if you don't? |
| Q3 |
You have 10.0.0.0/8 and need exactly 1,000 subnets, each supporting at least 50 hosts. What prefix length do you use? Show your reasoning. |
| Q4 |
What is the difference between a |
| Q5 |
A router shows |