Components of a Topology Diagram

The network topology diagram is the second piece of documentation (after the network configuration table), and it is considered an essential part of any network baseline. This diagram is a graphical representation of the network that must illustrate all the devices and how they are connected. Physical and logical detail about the network are revealed using consistent notations and symbols. Figure 1-1 is an example of a network topology diagram. In Figure 1-1, you can see a network cloud symbol with the title Internet. A network cloud symbol is often used to represent a network that is under control of another group (or company, or autonomous system, and so on). At times, the network cloud symbol is used within a network topology diagram to show an area whose detail is outside the scope of the diagram.

The information displayed in the network topology diagram might correspond to different layers of the TCP/IP model. For example, to illustrate the important components of a network at the Internet layer (TCP/IP model), you might include IP addresses, subnet masks, and routing protocols (see Table 1-5).

NOTE Remember that a network topology diagram shows all the devices and how they are physically and logically connected. The device name, interface or port name, IP address, and routing protocol(s) are a few of its important components.

Components of a Topology Diagram 15

Figure 1-1 Network Topology Diagram fa1/1 - fa1/2 -




Lexington fa1/1 - fa1/2 - s1/1 -

Components Shown in This Network Topology Diagram:

• Interface or Port Name

• Layer 2 Encapsulation

• Routing Protocols fa1/1 - fa1/2 - s1/1 -


BGP 200

BGP 200

Table 1-5 Components of a Topology Diagram Classified Based on the TCP/IP Model




Device name

Media type

Data link

MAC address



Trunk or access/VLAN number


IP address

Subnet mask

Interface name

Routing protocol(s)

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