Network documentation that actually gets used

Everyone agrees documentation matters. Few teams keep it current. The problem is usually not laziness but ambition: a 60-page design document nobody updates. Small, focused documents that are quick to change get used, and documents that get used stay accurate.

The five documents every small network needs

1. A network diagram: one page showing sites, internet links, firewalls, core switches, wireless controllers and key servers. Physical and logical diagrams can be separate.
2. An IP and VLAN plan: every subnet, its VLAN ID, purpose, gateway and DHCP range. A spreadsheet is fine.
3. A device inventory: hostname, model, serial number, location, management IP, firmware version and support end date.
4. An access list: who has admin access to what, and how (named accounts, MFA, jump host). Never store the passwords themselves here; use a password manager.
5. Runbooks: short step-by-step guides for common or critical tasks: replacing a failed switch, restoring the firewall config, adding a new VLAN, what to do when the internet is down.

Habits that keep it accurate

• Update as part of the change, not after. A change is not finished until the documentation is updated.
• One home. Keep everything in one place everyone can find, such as a wiki or shared folder, with a clear structure.
• Dates and owners. Put "last reviewed" and an owner on every document.
• Quarterly review. Spend an hour each quarter checking the inventory against reality.
• Automate where you can. Scheduled config backups and simple scripts that export interface and neighbour information reduce manual work. Our note on automated config backups shows how.

Write for the person on call at 2 a.m.

Good runbooks assume the reader is tired and stressed. Use numbered steps, exact commands, expected output and what to do if it does not match. Put the most important contacts, such as the ISP support number and circuit IDs, on the first page.

Security matters too

Network documentation is valuable to attackers. Keep it in a system with access control and MFA, avoid emailing diagrams around, and remove sensitive details from anything shared with suppliers unless they need them.

Why it is good for your career

Clear documentation is one of the most visible signs of a professional engineer. It makes handovers smooth, audits painless and your own work easier to show in interviews. Our project documentation note and small office network mistakes post are good next reads.