Network diagrams are a critical component in the
documentation process for any network. Just as software
developers document their code for easier maintenance
and sharing, network engineers document networks by
building network diagrams. It is very important to have
accurate network diagrams, especially when
troubleshooting network issues. The network has
become a business differentiator for all companies, and
each second of downtime costs money. Having up-to-
date network diagrams makes it much easier and faster
to troubleshoot network issues and decrease the MTTR
(mean time to resolution) when problems arise.
Several different types of network diagrams can be
created, depending on what needs to be emphasized and
documented. Layer 1 network diagrams can be used to
show physical connections, including how network
devices are connected and what type of cables (twisted
pair, fiber optics, and so on) are being used. These
diagrams can also show patch panel port connectivity
and availability and everything else that is in the confines
of physical connectivity.
Layer 2 network diagrams contain information related to
all Layer 2 devices, protocols, and connectivity in a
network. Such a diagram shows all the switches in the
network and how they are interconnected, including how
the ports on one switch connect to the ports on another
switch, which VLANs are configured on each switch,
which ports are configured as trunks and what VLANs
are allowed on them, which ports are configured as port
channels, and any other Layer 2 information. Depending
on the size of the network, a Layer 2 diagram can be split
into multiple documents.