Interpreting a Network Diagram
Network diagrams are visual aids in understanding how a network is designed and how it operates. In essence, they are maps of the network. They illustrate physical and logical devices and their interconnections. Depending on the amount of information you wish to present, you can have multiple diagrams for a network. Most common diagrams are physical and logical diagrams. Other diagrams used in networking are sequence diagrams, which illustrate the chronological exchange of messages between two or more devices.
Both physical and logical diagrams use icons to represent devices and media. Usually, there is additional information about devices, such as device names and models.
Physical diagrams focus on how physical interconnections are laid out and include device interface labels (to indicate the physical ports to which media is connected) and location identifiers (to indicate where devices can be found physically). Logical network diagrams also include encircling symbols (ovals, circles, and rectangles), which indicate how devices or cables are grouped. These symbols further include device and network logical identifiers, such as addresses. These symbols also indicate which networking processes are configured, such as routing protocols and provide their basic parameters.
In the example, you can see interface labels” S0/0/0,” “Fa0/5,” and “Gi0/1.” The label is composed of letters followed by numbers. Letters indicate the type of an interface. In the example, “S” stands for Serial, “Fa” stands for Fast Ethernet, and “Gi” for Gigabit Ethernet.
Devices can have multiple interfaces of the same type. The exact position of the interface is indicated by the numbers that follow, which are subject to conventions. For instance, the label S0/0/0 indicates serial port 0 (the last zero in the label), in the interface card slot 0 (the second zero) in the module slot 0 (the first zero).
The name Fast Ethernet indicates an Ethernet link with the speed of 100 Mbps.
The diagram also includes the Internet protocol version 4 (IPv4) address of the entire network given by 192.168.1.0/24. This number format indicates not only the network address, which is 192.168.1.0 but also the network’s prefix, a representation of its subnet mask, which is /24. IPv4 addresses of individual devices are shown as “.1” and “.2.” These numbers are only parts of the complete address, which is constructed by combining the address of the entire network with the number shown. The resulting address of the device in the diagram would be 192.168.1.1.