Network diagrams are not only handy to have, but provide a vital look at the network topology for your team, your company, and your peace of mind. Let’s look at what a network diagram is, and why it’s so important.

What is a network diagram?

A network diagram is, simply put, a schematic or map of your existing network that illustrates the nodes and their connections. Network diagrams are very useful at mapping out your elements and device interactions, as well as illustrating different network topology types.

You can map your network manually using pencil and paper, or with a drawing program like Visio. You might also use automated software tools to help you. It’s a lot easier with software tools like Auvik, which can provide powerful network topologies that update in real-time.

If you’re new to networking, you’re probably adopting an existing network that’s already deployed. You’ve probably discovered that the network is there to support your end users’ connectivity to applications and resources that they need to be productive. It might involve an internet connection, a firewall, switches, and end-user devices. In many organizations, there could be a separate person responsible for each of these areas.

Physical network diagrams vs. logical network diagrams: What’s the difference?

Network diagrams come in different shapes and sizes, but can generally be classified as either a physical network diagram or a logical network diagram. It’s important to recognize the difference between these two diagram types, as they communicate different information.

When talking about network topology, we’re mostly interested in the bottom few layers of the OSI model.

Layer 1 is the physical layer of the OSI model. For network design purposes, this means the things you can touch: the cables and the equipment. But it technically also includes the electrical and optical signaling properties. Layer 1 defines the properties of the cables that are necessary to carry the signals. Layer 1 also worries about wireless signaling used.

As network designers, we need to make sure we get the right cables to the right places and watch out for distance limitations. And of course, we need to make sure the right devices are physically connected to one another.

So when looking at physical network diagrams, you will often see devices like firewalls, switches, routers, and access points, along with a representation of the physical connections between them.

Layer 2 is the logical layer of the OSI model. Logical network diagrams represent network topologies at higher levels. For example, Layer 3 network diagrams depict routing paths, including static routes, and may indicate BGP peers. While some logical diagrams do include physical attributes, it’s not a requirement, and many logical network diagrams exclude items like physical link details, and occasionally even whole groups of devices, like underlying switch infrastructure.

The importance of network diagrams

As a network administrator responsible for the network, it’s vitally important you have a detailed understanding of your network topology. Without this information, even basic troubleshooting can be unnecessarily difficult. You’ll find that troubleshooting is much easier if you have detailed and up-to-date network documentation.

The important thing is to be clear in your mind about what information you’re trying to convey. It’s better to draw several diagrams that show different aspects of the same network than to try to put everything on one sheet of paper.

Understanding network diagram symbols

There are some useful shorthand symbols you can use when creating network diagrams. While there aren’t any universal rules, here’s a list of general best practices to help you accurately communicate networking ideas with colleagues, particularly useful for drawing network topologies on a whiteboard:

  • Draw Layer 3 network devices as circles.
  • Draw Layer 2 devices as rectangles.
  • Triangles represent multiplexer devices, which used to be more common in network diagrams. So instead, try using triangles for IP phones.
  • Everything else can be represented as a square or a rectangle, intended to represent a generic box.

Each symbol can also have a specific marking within it that indicates exactly which type of device it is. If you’re creating network diagrams using a drawing program, or your map is being automatically generated by a software tool, the symbols will be much more elaborate. But when these figures are drawn on a whiteboard, you can use simple symbols such as an X for a router or > for a firewall.

Here’s a table covering some of the most widely used symbols as they appear if you were to hand draw them, use a drawing program like Visio, and how we represent them in Auvik.

Source: Auvik Networks

Common network diagram symbols: a quick reference guide

  • Cloud. Clouds are used to summarize parts of the network that aren’t important for the diagram. This could mean the Internet or a WAN or even a collection of internal network segments like user VLANs.
  • Firewall. In software-generated or very detailed diagrams, a firewall is typically represented with a brick wall, to denote that it is a stop or checkpoint in your network data flow.
  • Terminal. Can be represented by a variety of end-user systems, but is typically represented by a computer.
  • Switch. As a Layer 2 object, switches are represented by crossed arrows, denoting the flow of data and the “switching” taking place between devices. Note: while a router and a Layer 3 switch can perform similar functions, it’s important to distinguish a device doing the Layer 3 routing, so it would not be represented by a switch symbol.
  • Bridge. A representation similar to a physical road bridge is often used to represent a networking bridge.
  • Server. Traditionally represented by a computer tower, a server is noted on a diagram as a node with data flowing towards other sources on the network.
  • Router. Routers can be represented by a variety of objects, but are usually rendered as boxes into which data enters and is distributed out through multiple destinations. A layer 3 switch can also use a similar symbol if it is providing a similar function as a router.
  • Peripheral device. The term peripheral device refers to all hardware components that are attached to a computer, such as a mouse, keyboard, or USB drive, and are represented by a symbol that matches their specific function.
  • Mainframe. A mainframe computer is legacy computer architecture used primarily by large organizations for a critical line of business applications and bulk data processing.
  • Hub. Similar to a switch, a hub can be represented as any network hardware device for connecting multiple Ethernet devices together and making them act as a single network segment.

5 types of network topologies

If you’ve ever studied the history of networking, you’re likely familiar with many of the following network topologies. When designing a network today, realize that many of the following topologies, such as a ring and bus topologies, are no longer considered an efficient way of architecting a network.

  1. Ring topology

    Features three or more interconnected switches. Each switch in a ring topology is connected to two neighboring switches, one upstream, the other downstream. The last switch is connected back to the first to form a circle (or ring). Any one device or link can fail without disrupting connectivity for any of the others.

  2. Bus topology

    With a single transmission line for all nodes, bus topology is the simplest kind of topology in which a common channel (or bus) is used for communication in the network.

  3. Star topology

    A network topology in which all the nodes are connected to a centralized hub. These networks scale very well because you can increase the size of the hub by creating a ring of hub routers as the routing core.

  4. Mesh topology

    A computer network topology in which nodes connect directly, dynamically, and non-hierarchically to as many other nodes as possible and cooperate to efficiently route data. Mesh networks dynamically self-organize and self-configure, which can reduce installation overhead.

  5. Tree topology

    A combination of bus and star topologies, a computer network topology in which all nodes are directly or indirectly connected to the main cable.

Examples of network diagrams

A network diagram built with Auvik
A network diagram built with Visio
A hand-drawn network diagram

How network diagrams can benefit organizations

There are several positive benefits from creating and maintaining good network diagrams.

First, network diagrams are a critical part of any change management process. If you ever need to change anything, like adding a new switch or a new link to a remote office, you’ll need good documentation to understand how the traffic will flow through these new pieces of the network. This will help ensure the new network is stable and efficient.

Second, network diagrams are a key piece of documentation required for compliance. Auditors, such as those for PCI compliance, always want to see that you’ve accurately documented and diagramed your network topology. Specifically, they need to know where the firewalls, switches, and server resources are, and all the different ways that someone could get into the network.

If you ever need to submit this kind of information to an external audit, or if there were ever a serious problem with your network and you needed to defend the design to management or bring in external consultants, having good and current diagrams will always help your case.

Finally, network diagrams are a valuable component of any network troubleshooting process. When you’re faced with a “network is slow” or “network is down” problem, whether reported by a user or noticed by your network management software, having updated network diagrams allows you to immediately understand the context behind the issue. This includes what servers, applications, and users may be impacted, along with the relevant network devices along the logical and physical paths to help direct and accelerate your troubleshooting.

Good network diagrams are not difficult to make but can be a time-suck due to the commitment required to discover and inventory all of the assets in the network. Because of this, up-to-date and accurate network diagrams are a rare find.

Auvik is a particularly useful tool for automated network mapping. It does a comprehensive job of laying out your network topology with endpoint-level visibility, far deeper than most other systems and manual topology maps. Reacting to network changes as they happen, Auvik’s network topology maps ensure you always have the up-to-date network topology at your fingertips.

Auvik can map most networks and have monitoring fully enabled in less than 30 minutes. See for yourself on your network. Get your free 14-day Auvik trial here.

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