Now that we have explained the purpose and suggested components for a network topology
diagram, let’s go through the steps to create one.
We will begin with an examination of the standard set of symbols used in such diagrams.
By now, most of you will have already seen and know these symbols; they are illustrated in
Figure 34.3. Employing a standard set of symbols for device types helps to ensure that any
new network administrators coming into the environment will be able to easily understand
the documentation.
FIGURE 3 4 . 3 Networking symbols
In most cases, a network topology diagram is created after the network configuration tables
are set up, because the topology diagram uses much of the information contained in the configuration
tables. Figure 34.4 illustrates a sample network topology diagram and its relationship
to some of the information used from the router configuration table.
Similarly, there is also a direct correlation between items on the topology diagram and the
switch network configuration table, as illustrated in Figure 34.5.
Because most of the information that is on the network topology diagram has already been
retrieved and placed in the network configuration tables, relatively few commands are needed
to generate the diagram itself. One command of great assistance is show cdp neighbors. The
Cisco Discovery Protocol (CDP) is a proprietary protocol that identifies directly attached Cisco
devices. This discovery is done at layer 2, so there is no need to have IP connectivity to see the
neighbors. The show cdp neighbor command shows the neighbors that have been learned via
CDP and gives their summary information. More detailed information can be found by using
the show cdp neighbors detail command.