11.7.5 Packet Tracer - Subnetting Scenario

11.7.5 packet tracer - subnetting scenario is a hands‑on lab that guides students through designing and implementing subnets using Cisco Packet Tracer, reinforcing IP address planning, VLSM, and routing basics. This scenario mimics a small corporate network where multiple departments require distinct subnets, and the learner must allocate address spaces, configure routers, and verify connectivity. By the end of the exercise, participants will understand how to calculate subnet masks, apply Variable Length Subnet Mask (VLSM), and test end‑to‑end communication within a simulated environment.

Overview of the Scenario

The exercise is set in a multi‑building campus where each building houses a different department: HR, Finance, IT, and R&D. Each department needs its own subnet to isolate traffic, while a Server subnet provides shared services. The topology includes:

• Four separate LAN segments (one per department)
• A central Core Router that interconnects all segments
• A Layer‑3 Switch that aggregates traffic before forwarding to the Internet
• A DHCP Server that supplies IP addresses dynamically

The goal is to design a scalable addressing scheme that meets the following requirements:

1. HR: 30 hosts
2. Finance: 60 hosts
3. IT: 120 hosts
4. R&D: 200 hosts
5. Servers: 50 hosts

The lab also emphasizes documentation of the subnet plan, verification of routing tables, and troubleshooting common misconfigurations.

Prerequisites

Before starting, ensure you have a basic understanding of:

• IP addressing and binary‑to‑decimal conversion
• Subnet mask calculation using VLSM
• Cisco Packet Tracer navigation and device placement
• Command‑line interface (CLI) commands for router and switch configuration

Familiarity with terms such as CIDR, default gateway, and static routing will accelerate the learning process.

Step‑by‑Step Configuration

1. Determine the Addressing Scheme 1. Calculate total required hosts: 30 + 60 + 120 + 200 + 50 = 460 hosts.

2. Select a network address: Use the private range 192.168.10.0/24 as the base.
3. Apply VLSM to allocate subnets in descending order of size:

Note: The above table demonstrates a simplified allocation; in practice you would choose larger prefixes (e.g., /26 or /25) to accommodate the host counts. Adjust the calculations accordingly.

2. Create VLANs on the Layer‑3 Switch

• Access VLAN 10 for HR
• Access VLAN 20 for Finance
• Access VLAN 30 for IT
• Access VLAN 40 for R&D
• Access VLAN 50 for Servers

Configure VLANs using the CLI:

Switch(config)# vlan 10
Switch(config-vlan)# name HR
Switch(config)# vlan 20Switch(config-vlan)# name Finance
...

3. Assign Switch Ports to VLANs

• Connect each department’s PCs to the corresponding access ports.
• Verify port assignments with show vlan brief.

4. Configure the Core Router

a. Enable Routing

Router(config)# ip routing

b. Configure Sub‑Interfaces for Each VLAN

Router(config)# interface GigabitEthernet0/0.10
Router(config-subif)# encapsulation dot1Q 10
Router(config-subif)# ip address 192.168.10.1 255.255.255.0
Router(config-subif)# no shutdown
...

Repeat for VLANs 20‑50, adjusting the sub‑interface number and IP address to match the allocated subnet.

c. Set Up Default Route to the Internet

Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.10.254

(Assuming the ISP connection is on the same interface.)

5. Deploy DHCP

Create a DHCP pool for each VLAN:

Router(config)# ip dhcp pool HR
Router(dhcp-config)# network 192.168.10.0 255.255.255.0
Router(dhcp-config)# default-router 192.168.10.1Router(dhcp-config)# dns-server 8.8.8.8

Repeat for Finance, IT, R&D, and Servers, ensuring each pool uses the correct subnet and default gateway.

6. Verify Connectivity

• Ping tests between hosts in different VLANs.

• Traceroute to confirm routing paths.

• Check DHCP lease assignments with show ip dhcp binding.

• Validate Internet access from devices in each VLAN.

7. Document and Maintain

Record the VLAN-to-department mappings, IP address allocations, and DHCP configurations in a network diagram. Regularly review logs and monitor traffic to ensure optimal performance and security.

Conclusion

By systematically applying VLSM, creating dedicated VLANs, configuring sub-interfaces on the core router, and deploying VLAN-specific DHCP pools, you establish a scalable, secure, and efficient network. This approach not only meets the immediate needs of each department but also provides a foundation for future expansion and streamlined network management.

In practice, you would choose larger prefixes (e.g., /26 or /25) to accommodate the host counts. Adjust the calculations accordingly.

2. Create VLANs on the Layer‑3 Switch

• Access VLAN 10 for HR
• Access VLAN 20 for Finance
• Access VLAN 30 for IT
• Access VLAN 40 for R&D
• Access VLAN 50 for Servers

Configure VLANs using the CLI:

Switch(config)# vlan 10
Switch(config-vlan)# name HR
Switch(config)# vlan 20
Switch(config-vlan)# name Finance
...

3. Assign Switch Ports to VLANs

• Connect each department's PCs to the corresponding access ports.
• Verify port assignments with show vlan brief.

4. Configure the Core Router

a. Enable Routing

Router(config)# ip routing

b. Configure Sub-Interfaces for Each VLAN

Router(config)# interface GigabitEthernet0/0.10
Router(config-subif)# encapsulation dot1Q 10
Router(config-subif)# ip address 192.168.10.1 255.255.255.0
Router(config-subif)# no shutdown
...

Repeat for VLANs 20-50, adjusting the sub-interface number and IP address to match the allocated subnet.

c. Set Up Default Route to the Internet

Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.10.254

(Assuming the ISP connection is on the same interface.)

5. Deploy DHCP

Create a DHCP pool for each VLAN:

Router(config)# ip dhcp pool HR
Router(dhcp-config)# network 192.168.10.0 255.255.255.0
Router(dhcp-config)# default-router 192.168.10.1
Router(dhcp-config)# dns-server 8.8.8.8

Repeat for Finance, IT, R&D, and Servers, ensuring each pool uses the correct subnet and default gateway.

6. Verify Connectivity

• Ping tests between hosts in different VLANs.
• Traceroute to confirm routing paths.
• Check DHCP lease assignments with show ip dhcp binding.
• Validate Internet access from devices in each VLAN.

7. Document and Maintain

Record the VLAN-to-department mappings, IP address allocations, and DHCP configurations in a network diagram. Regularly review logs and monitor traffic to ensure optimal performance and security.

Conclusion

By systematically applying VLSM, creating dedicated VLANs, configuring sub-interfaces on the core router, and deploying VLAN-specific DHCP pools, you establish a scalable, secure, and efficient network. This approach not only meets the immediate needs of each department but also provides a foundation for future expansion and streamlined network management.

In practice, you would choose larger prefixes (e.g., /26 or /25) to accommodate the host counts. Adjust the calculations accordingly.

2. Create VLANs on the Layer‑3 Switch

• Access VLAN 10 for HR
• Access VLAN 20 for Finance
• Access VLAN 30 for IT
• Access VLAN 40 for R&D
• Access VLAN 50 for Servers

Configure VLANs using the CLI:

Switch(config)# vlan 10
Switch(config-vlan)# name HR
Switch(config)# vlan 20
Switch(config-vlan)# name Finance
...

3. Assign Switch Ports to VLANs

• Connect each department's PCs to the corresponding access ports.
• Verify port assignments with show vlan brief.

4. Configure the Core Router

a. Enable Routing

Router(config)# ip routing

b. Configure Sub-Interfaces for Each VLAN

Router(config)# interface GigabitEthernet0/0.10
Router(config-subif)# encapsulation dot1Q 10
Router(config-subif)# ip address 192.168.10.1 255.255.255.0
Router(config-subif)# no shutdown
...

Repeat for VLANs 20-50, adjusting the sub-interface number and IP address to match the allocated subnet.

c. Set Up Default Route to the Internet

Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.10.254

(Assuming the ISP connection is on the same interface.)

5. Deploy DHCP

Create a DHCP pool for each VLAN:

Router(config)# ip dhcp pool HR
Router(dhcp-config)# network 192.168.10.0 255.255.255.0
Router(dhcp-config)# default-router 192.168.10.1
Router(dhcp-config)# dns-server 8.8.8.8

Repeat for Finance, IT, R&D, and Servers, ensuring each pool uses the correct subnet and default gateway.

6. Verify Connectivity

• Ping tests between hosts in different VLANs.
• Traceroute to confirm routing paths.
• Check DHCP lease assignments with show ip dhcp binding.
• Validate Internet access from devices in each VLAN.

7. Document and Maintain

Record the VLAN-to-department mappings, IP address allocations, and DHCP configurations in a network diagram. Regularly review logs and monitor traffic to ensure optimal performance and security.

Conclusion

By systematically applying VLSM, creating dedicated VLANs, configuring sub-interfaces on the core router, and deploying VLAN-specific DHCP pools, you establish a scalable, secure, and efficient network. This approach not only meets the immediate needs of each department but also provides a foundation for future expansion and streamlined network management.