Creating Network Diagrams Using Cisco Packet Tracer.

6 min readJul 29, 2023

(Last Updated: 23rd March, 2024)

An effective network design is crucial for seamless communication and data flow. The hierarchical approach is the most effective technique for designing and implementing successful network topologies in Cisco Packet Tracer.

The first step involves identifying the network layers: Layer 1, Layer 2, and Layer 3. At Layer 1, we can incorporate devices such as enterprise routers and Layer 3 switches, which ensure efficient communication within the network topology.

Below is a step-by-step guide to implementing successful network topologies in a simulation environment:

Step 1:

Define and identify the requirements before tackling the design, network’s purpose, size, and expected traffic load. List any specific security, redundancy, or performance requirements.

Network Purpose:

Define the primary objective of the network. For instance, it could be to provide internet access to an office or facilitate data sharing.

Network Size:

It could be a local area network (LAN) within a building or a wide area network (WAN) connecting multiple geographically dispersed locations.

Expected Traffic Load:

Consider factors like data transfer rates, concurrent users, peak usage hours, and bandwidth requirements.

Number of Users, Devices, and Services:

Identify the number of end-users who will utilize the network, e.g., computers, printers, and the range of services, such as emailing, VoIP, etc.

Security Requirements:

It may involve defining access controls, encryption standards, firewall configurations, intrusion detection, and prevention mechanisms.

Redundancy Requirements:

Assess the level of redundancy necessary for critical components like switches, routers, and power supplies.

Performance Requirements:

Define the expected performance metrics, such as latency, throughput, and response times.

Step 2:

Divide the network into logical segments based on different departments, functions, or security levels. It will help manage traffic flow and implement security measures more efficiently.

segments in a network i.e. blocks & departments

Step 3:

Choose appropriate Cisco devices for your network, such as routers, switches, firewalls, and access points.

Consider factors like port density, throughput, and compatibility with future upgrades.

Note: Ensure the selected devices support the necessary protocols (e.g., IPv4/IPv6, OSPF, VLAN, etc.) for your network requirements.

Step 4:

Create a Physical Layout. Start by placing devices on the Packet Tracer workspace. Drag and drop routers, switches, and PCs onto the canvas. Organize them logically based on their location in the physical setup.

dragging and dropping devices on the packet tracer workspace

Step 5:

Assign and configure IP addresses to devices on the network. Decide whether to use static or dynamic IP addressing (DHCP).

Use subnetting to manage IP addresses and control broadcast domains for large networks.

interface (FastEthernet0/1) IP configuration

Step 6:

Set up routing protocols. Configure appropriate routing protocols like OSPF or EIGRP if your network requires dynamic routing.

Example:

We have two routers that need to be configured using OSPF protocol.

Router 1:

FastEthernet0/0: IP address 192.168.1.1/24
Loopback0: IP address 10.0.0.1/32

Router 2:

FastEthernet0/0: IP address 192.168.1.2/24

Now, let’s configure OSPF between these routers:

Explanation:

Router> and Router# are the prompts, indicating user EXEC mode and privileged EXEC mode respectively.
enable command enters privileged EXEC mode.
configure terminal (or conf t) enters global configuration mode.
router ospf 1 starts OSPF configuration with process ID 1.
network <network-address> <wildcard-mask> area <area-id> specifies the networks to participate in OSPF with their respective areas.
end exits back to privileged EXEC mode.
show ip ospf interface brief displays a summary of OSPF-enabled interfaces and their status.
show ip route shows the routing table, displaying the learned routes.

Note: Make sure to adapt the IP addresses, interfaces, and OSPF areas based on your network setup.

Step 7:

Implement Security Measures Enhance network security by configuring access control lists (ACLs), SSH (Secure Shell), port security, and virtual LAN (VLAN) segmentation.

Consider implementing firewalls and intrusion prevention systems (IPS) for added protection.

port security configuration on FastEthernet0/1

Explanation:

Switch> and Switch# are the prompts, indicating user EXEC mode and privileged EXEC mode respectively.
enable command enters privileged EXEC mode.
configure terminal (or conf t) enters global configuration mode.
interface FastEthernet0/1 enters the interface configuration mode for the specific port.
switchport port-security enables port security on the interface.
switchport port-security maximum 1 sets the maximum number of allowed MAC addresses.
switchport port-security violation restrict configures the violation action as "restrict."
switchport port-security mac-address sticky enables sticky MAC address learning, automatically adding the first MAC address seen on the port.
end exits back to privileged EXEC mode.
show port-security interface FastEthernet0/1 displays the port security configuration and current status for the interface.

Note: To reduce the attack surface, change the default passwords on devices, enable SSH (Secure Shell) for secure remote access, and disable unused ports.

Step 8:

Test connectivity between all devices to ensure proper communication across different segments. Connectivity can be tested through physical and non-physical methods.

Physical testing methods:

Ping Test:

It sends a small packet (ICMP echo request) to a target device and waits for an ICMP echo reply. Successful ping responses indicate connectivity and round-trip time, while failures indicate potential issues.

Link Lights and Physical Inspection:

Physically inspecting network equipment (routers, switches, etc.) to ensure that link lights are active and showing the appropriate connection status (e.g., solid green for active connections, blinking for activity).

Cable Testing:

Using cable testers to verify the integrity of network cables, identifying faults like open circuits, shorts, or incorrect wiring.

Tone and Probe Testing:

Identifying and tracing cables by sending a tone signal through a cable and using a probe to locate the corresponding cable end.

Non-physical methods:

Port Scanning:

Scanning the target device’s ports to check which ones are open, closed, or filtered. This helps identify potential services running on the device and can reveal security vulnerabilities.

Network Testing Software:

Utilizing specialized network testing tools and software to assess network performance, bandwidth, and latency. Examples include iPerf, Speedtest, and Wireshark.

Traceroute:

Tracing the network path taken by packets from the source to the destination, identifying the route and potential points of failure.

Loopback Testing:

Loopback interfaces or addresses can be used to test the functionality of a device’s network stack. This can be valuable for testing the device without external connectivity.

Protocol-specific Testing:

Protocol-specific testing tools can ensure proper configuration and connectivity for more advanced setups, such as virtual LANs (VLANs), MPLS (Multiprotocol Label Switching), or VPN (Virtual Private Network).

Step 9:

Create comprehensive network documentation that includes device configurations, IP addresses, VLAN assignments, routing tables, and security settings for reference.

Note: Keep the documentation up-to-date as you make changes or upgrades to the network.

Designing a network topology in Cisco Packet Tracer requires careful planning, and it’s crucial to consider scalability and future growth.

To maintain an efficient and robust network infrastructure, regularly review the network’s performance, security, and adherence to business requirements.

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