Network Documentation: Building a Network Diagram

A current, accurate network diagram is essential for troubleshooting, onboarding new IT staff, and planning changes. A good diagram shows all devices, their connections, IP addresses, and VLANs at a glance. Tools: Microsoft Visio (comprehensive, paid), draw.io / diagrams.net (free, browser-based, excellent for most needs), Lucidchart (cloud-based, collaborative). For automated discovery, tools like SolarWinds NNM or open-source alternatives can auto-generate topology diagrams from SNMP data. What to include: internet connection (ISP, circuit ID, bandwidth), modem/ONT, firewall, core switch, distribution switches, access switches (with patch panel port numbers), wireless APs, servers (with IPs and roles), and VLAN boundaries. Use standard network symbols for consistency. Store the diagram in a shared location (SharePoint, IT documentation tool like IT Glue) and update it whenever the network changes. An outdated diagram is worse than none — it misleads rather than helps.