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Logical vs. physical topology: What's the difference?
A complete network topology is a network map that provides a look into the network's hardware components and data flow using physical and logical topologies.
Networks are the backbone of the digital economy. To better understand their networks, network engineers must use a network topology.
A network topology is the physical and logical layout that illustrates how a network functions. It serves as a map, guiding engineers just as a city map guides tourists. Without a topology, network structure and performance are difficult to understand, making optimization a challenge.
Logical topology vs. physical topology
As previously stated, network topology is analogous to a city map. To better understand logical and physical topologies, equate them to how a city functions.
Imagine a city and its physical makeup -- streets, buildings and infrastructure, such as traffic lights and crossroads. Similarly, a network's physical makeup includes different devices. In this analogy, the streets are the physical cables and wires. The buildings are the servers, computers and other network devices. The infrastructure, such as traffic lights and crossroads, are the routers and switches.
But cities aren't only made up of buildings and streets. Traffic flows through cities to get to different destinations, often in different neighborhoods. Traffic flow is the data flow, and network protocols are the rules traffic must follow. Neighborhoods are equivalent to virtual LANs (VLANs) and subnets.
In this analogy, the physical layout of the city -- the way the streets are planned, the building locations and how they connect to roads -- represents the physical topology. Physical topology is a tangible way to observe network components and their physical connections. Meanwhile, the city's internal activity represents the logical topology. Logical topology is how data moves through the network.
Key differences
Below is a breakdown of the major differences between physical and logical topologies.
| Physical topology | Logical topology |
| Physical network connection | Network data flow path |
| Illustrates the network's physical layout | Represents the network logistics related to data transmission |
| The real route involved with data transmission | The real representation of data flow |
| Significantly affects device selection due to cost, scalability and bandwidth | Affects the speed and data flow of packets |
| Can modify the layout any time based on evolving network needs | Does not involve any manual effort |
Improving topology layouts
Network engineers can improve their network layouts with some strategies for better performance and scalability.
Consider both the physical and logical topology during network planning and design. Network architects should ensure that the physical and logical topology work together to meet network goals. The physical layout should support the expected connection, considering factors such as the following:
- Device cost.
- Cable length.
- Ease of installation.
When it comes to the logical layout, design networks to optimize data flow based on protocol, addressing and routing. Optimizing the logical topology is simple, thanks to VLANs, quality of service policies and better resource management.
Define the path
Logical topology is an abstract network representation, illustrating how devices communicate and data flows between them. Common logical topologies include the following:
- Bus topology.
- Ring topology.
- Star topology.
- Mesh topology.
Factors such as network protocols, addressing schemes and routing protocols all influence network structure. These factors collectively determine the efficiency and reliability of data transmission within the network.
How network engineers enable the logical topology
Network engineering is an ecosystem full of various tasks. Network architects are crucial in shaping and implementing logical topology when designing networks. They ensure the topology meets their organization's needs with efficient and reliable communication across the network. Here are some steps they can follow to do so:
- Create a visual presentation. A logical topology diagram visualizes the data flow path and explains how devices interact with the network.
- Implement protocols and addressing. Network architects select particular network protocols to resolve a problem and a clear addressing schema that supports efficient data transmission.
- Optimize performance. By observing the traffic patterns, it's possible to adjust the logical topology and enhance performance and reliability.
Verlaine Muhungu is a self-taught tech enthusiast, DevNet advocate and aspiring Cisco Press author, focused on network automation, penetration testing and secure coding practices. He was recognized as a Cisco top talent in sub-Saharan Africa during the 2016 NetRiders IT Skills Competition.
