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Physical topology is the actual layout of a network: where devices sit and which cables, ports, and links connect them. Logical topology is how the network communicates: the relationships between devices, the addresses, segments, and routes that govern traffic, and the path data follows, regardless of where the hardware is placed. A physical diagram answers “What is plugged into what?” A logical diagram answers “How does traffic move?” One network can have a single physical arrangement and a quite different logical structure, so the two views answer related but separate questions.
Physical topology: the layout you can trace with your hands
A physical topology describes actual device placement and physical links. Cisco defines it in terms of real connections and the placement of components (Cisco, what is network topology). Cisco Networking Academy training material hosted by Universitas Sriwijaya lists the details a physical diagram should carry:
![Computer Networking Bible: [3 in 1] The Complete Crash Course to Effectively Design, Implement and Manage Networks. Including Sections on Security, Performance and Scalability](https://m.media-amazon.com/images/I/41H4YJnxKgL._SL160_.jpg)
- Device location and type, including model and operating system version
- Cable type, cable identifier, and cable specification
- Connector type and the cable endpoints at each end of a link
- Ports, racks, servers, and other hardware
Use this view when you need to trace a cable, identify which port a device uses, check how equipment is laid out in a room or rack, or narrow down a problem at the physical layer. The training material is course content rather than a current Cisco product specification, and it does not show a clear publication date, so treat its field list as a reliable guide to what a physical diagram is for, not as a description of how current hardware is configured (Cisco Networking Academy course material).
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A logical topology describes communication relationships and the route data takes between devices. Microsoft’s guidance on network diagrams describes logical diagrams as showing how devices talk to each other, which subnets and segments they belong to, and how routing is arranged (Microsoft). The Cisco Networking Academy material lists the typical contents of a logical diagram:
- Device identifiers and interface identifiers
- IP addresses and prefix lengths
- Connection type, including site-to-site VPNs and WAN technologies
- Routes and the routing and data-link protocols in use
- Subnets and network segments
Use this view when you are asking how two devices reach each other, which segment a host belongs to, or where traffic is directed. Because it is built from addressing and routing, it is the view that explains behavior that a cable map cannot show.
Why the two views can disagree
The physical infrastructure carries the traffic, but the logical behavior is set by network configuration, not by where the hardware sits. Two devices that share a switch can belong to different subnets, in which case they cannot exchange traffic directly and must go through a router. Two devices in separate rooms can share a segment. Physical proximity alone does not tell you which segment a device is in or how a packet will travel.
Cloud networking makes the separation explicit. Virtual networks have logical topologies that are independent of the physical topology underneath them (AWS, network topology). The underlying hardware still matters, though: Cisco notes that a logical design relies on a physical underlay with enough capacity and scalability to support it (Cisco). A logical diagram is therefore not a floor plan, and a physical diagram is not a traffic map.
Side-by-side comparison
| Aspect | Physical topology | Logical topology |
|---|---|---|
| Question it answers | What is plugged into what? | How does traffic move, and which devices can reach each other? |
| Typical detail | Devices, cables, ports, connectors, endpoints | Addresses, prefixes, interfaces, subnets, segments, routes, protocols |
| Best used for | Cable tracing, port identification, physical-layer troubleshooting | Addressing, routing, segmentation, VPN and traffic analysis |
| Changes when | Hardware is moved, recabled, or replaced | Addressing, routing, or segmentation is reconfigured, even if no cable moves |
| Common misreading | Assuming a cable run shows which network segment a device belongs to | Assuming the diagram shows where equipment or cables physically are |
A worked example: an Ethernet star
An Ethernet network can use a star layout, with each endpoint cabled to a central switch. The physical diagram shows that star clearly: every cable runs to one device in the middle. The logical diagram answers different questions. Which endpoints share a subnet? Where does a packet go when it leaves one segment for another? Which router or gateway handles traffic leaving the local network? Those answers may not be visible from the cabling at all.
Consider two laptops connected to the same switch. The physical diagram shows them side by side. If one laptop is on 192.168.1.0/24 and the other is on 192.168.2.0/24, the logical diagram shows that they cannot talk directly; traffic between them must pass through a router. Reading only the physical diagram would suggest a direct path that does not exist.
Common topology forms and how to compare them
Bus, ring, star, tree, mesh, and hybrid are structural patterns, and AWS also describes point-to-point links (AWS). These names describe shapes, so they do not by themselves tell you whether a drawing is physical or logical. What matters is whether the diagram shows actual connections or communication paths.
| Form | Behavior AWS describes | Main trade-off |
|---|---|---|
| Bus | Simple, with all devices sharing a central bus | Vulnerable to failure of the bus itself, and congestion grows as devices are added |
| Star | Each device connects to a central switch | Easy to isolate one endpoint or cable when it fails, but dependent on the central switch |
| Mesh | Devices interconnect through multiple paths | Fault tolerant, but harder to configure and expand |
AWS presents these as general tendencies rather than guarantees; real behavior depends on implementation and redundancy. When choosing among actual topology options, compare them on these axes:
- Failure behavior and redundancy: what happens if a link, node, or central device fails, and whether alternate paths exist
- Performance: where capacity limits or bottlenecks will appear
- Scalability and change: how easily capacity, users, sites, or segments can grow
- Cost and complexity: equipment, installation, cabling, maintenance, and expansion demands
- Security and purpose: the access control, segmentation, and resilience the workload requires
Cisco recommends weighing purpose, scale, budget, performance, redundancy, and scalability together (Cisco).
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which view to consult when something breaks
- A cable, port, or link appears dead: start with the physical diagram to find the cable type, identifier, and endpoints, then check the port at each end.
- Two devices on the same switch cannot reach each other: the physical view will not show why. Check the logical view for subnet membership, prefix lengths, and whether a router is required between segments.
- Traffic takes an unexpected path: use the logical view to examine routes, routing protocols, and any site-to-site VPN connections.
- A WAN or cloud network behaves differently from what the cabling suggests: the logical view is the right starting point, because the traffic path is defined by configuration rather than cable runs.
How to build the right diagram
Microsoft advises using both kinds of diagram as appropriate and says the detail level can range from individual devices to services or larger network areas. If one drawing becomes too dense, split it into focused views. In its words, “Both types of network diagrams have their place, and you’ll probably use both.” The Microsoft 365 team wrote that guidance; the page does not name an individual author or give an exact publication date in the accessed content.
- Decide whether the reader needs hardware placement, communication behavior, or both.
- List the devices and services relevant to that question.
- Arrange physical components or logical relationships in a readable layout.
- Add connections and label what each line means. Do not assume every line represents the same kind of link.
- Include the matching detail: cable endpoints and identifiers on a physical view; addresses, segments, and routes on a logical view.
- Check that connections and labels are correct, then split the diagram into focused views if it is hard to follow.
Microsoft lists troubleshooting, planning, expansion, and security and compliance work as good reasons to keep an accurate network diagram (Microsoft).
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