A network diagram is essential for visualizing network design and network relativity.
Diagramming tools should have task specific libraries of readily identifiable graphics for routers, switches, printer, hubs, host, severs, wireless access points, power and storage, as well as making provisions for vendor-specific graphics (like the icons used by Cisco).
While Microsoft Visio is the major network diagramming software, and has become almost synonymous with network diagrams, there are other players in the field too. The main drawback of Visio 2003 and 2007 is the absence of the Auto discovery feature. Unless a separate add-on is purchased, neither versions can import existing directory structures like LDAP, Active Directory, or use SNMP polls to auto-discover devices and diagram the network.
But since the ubiquity of Visio makes it easily sharable within and between organizations (Visio does have definite pluses – the point and click Telnet access; the ability to track comments; publishing capabilities and so on), it’s worthwhile to invest in third-party network mapping software that can integrate Visio and auto discovery features.