Why your network diagrams suck (and they do, which is sad because it’s a fundamental IT need):
1. You don’t have any.
2. You pooped them out last week.
3. You tried to put everything on one drawing (VLANs, servers, network gear, port-specific connections, IP addresses, serials, virtualization…).
4. You didn’t include enough info to answer questions the diagrams are meant to answer.
5. You have too many diagrams and they conflict. (Also see next.)
6. You don’t update them as you make changes (if you update them at all).
7. You auto-generate them from some network scan tool or inventory tool, and they just look like ass no matter what you do (or don’t say enough to be meaningful).
8. They all look and feel completely different because 4 different people maintain their own diagrams for what they control.
9. You don’t make diagrams from the viewpoint of the intended audience. What works for you won’t work for your contractors, auditors, developers, security/comliance, customers.