Sample diagrams for networking: four topology diagrams, a layer model, and three UML sequence diagrams of the protocols every connection depends on. Each sample page draws one realistic scenario, explains it step by step, shows a variant, and gives the diagram as code.
1. Which Diagrams Networking Uses
Networking work asks three kinds of question, and each has its own diagram. Where are the devices, links and security zones? That is a topology diagram. What wraps what, and at which layer does a protocol or device operate? That is a layer stack. What happens, in what order, when two hosts talk? That is a UML sequence diagram.
Only the sequence diagrams here are UML. UML covers software structure and behaviour; topology, security-zone and layer diagrams are the other standard notations used alongside it, and network engineers expect them. The closest UML equivalent of a topology diagram is the deployment diagram, but in practice teams draw labelled device boxes and links, grouped by VLAN, subnet or zone, with colour reserved for meaning: green for allowed flows and trusted zones, yellow for emphasis, red for blocked or failed paths.
2. Question to Diagram
Question
Diagram
Sample page
What is connected to what, and where are the trust boundaries?
Start from the question your reader has, not from the tool you like. If the answer involves time or round trips, draw a sequence; if it involves boundaries or capacity, draw a topology.
3. Conventions Used in These Samples
One box per device or role, labelled with its name and the one fact that matters (address, AS number, rule).
Dashed boundaries for VLANs, subnets, AZs and security zones.
Arrows only where direction matters (traffic flows); plain lines for links.
Every sample has a failure or alternative variant, because networks are designed around what breaks.
Every sample includes the diagram as code (Mermaid, PlantUML, Graphviz, D2 or Python diagrams) so it can live in version control.