Imagine I need to document and draw a topology diagram (related to layer 1-3) of an existing data center.

What approach do you use to perform such documentation? Do you go physically router by router (or switch by switch) to determine neighbor information with CDP neighbor command for example?

Assume I have no existing diagram for such network.

Once I get a picture of how the current environment is setup, I am planning to show this to a Cisco rep and discuss upgrade options.

Please let me know what you think.