There is software that (sort of) automatically creates so-called "network maps". In order for devices and capabilities to be discovered, the devices have to support management standards (these days, almost all PBXs and KSUs worth their salt do, but not all of them by default. With end-user terminals such as phones and faxes etc the picture is more unclear. IP phones all support SNMP though). By far the most common standard is SNMP, now in version 3.
The downside is that management applications have a steep learning curve due to complexity. There is software that does just network mapping but in my experience the price is too expensive, might as well get a full management app and be done with it. There are freebies though. I've used the following:
The Dude from Microtik software. Nice maps with some configuration options. Version 3 is in beta, which seems stable. You can download version 2 otherwise.
Spiceworks version 2. This is a browser-based program. Like the Dude, it's free, but you gett banner ads.
Good luck.
