Network Diagrams: Drawing Complex VLAN Networks With IP Addressing

In an earlier article I showed you how to create a simple VLAN image from a single line. I also talked about why using ONLY a line makes it more simple. If you need a recap go back to Network Diagrams: Labelling an VLAN/IP Segment (and the earlier article on the same topic Network Diagrams: VLANs and IP Subnets.

OK, got that in your head. I think we are ready to go on. Note: I assume that you have some experience in drawing diagrams and familiar with some of the hassles of representing a data network.

Drawing multiple VLANs and IP Subnets

For larger networks, you often have equipment that need to connect to multiple VLANs.

The problem is showing the all the connections in a meaningful way. Using straight lines ends up showing something like this:

If you use dynamic connectors, it will look completely useless as the right angles ends up invisible: Something like this:

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Understand the problem, don’t look at the solution

I think the problem here is that I like using the pretty Cisco router icons. You can’t get them to clearly represent the physical device with interfaces (either logical or physical). Well, you can for small and simple diagrams like thss one, the Cisco router icon kind of just works:

My problem is that I am looking at the solution, not the problem. In other words, how can I make the Cisco router icon have meaning for a more complicated diagram. The answer is not to the use the Cisco router thingie and make your own shape.

What sort of shape ?

Any shape you like really. My preference tends towards something like this:

Building this shape

1. Draw a simple box
2. Go Format, Line & change the colour of the line to a dark blue, and set rounded corners
3. Go Format, Fill & change the colour of the fill to pale colour

Labelling the Shape

There are a few ways of attacking this problem. When I think about the data that I need:

• The box needs at least name
• maybe to the loopback address if you are using loopbacks for management
• IP address
• interface name ie. for a Cisco Fa0/0

This data tends to two categories: details of the system, and details of the interface. I prefer click on the box to go into text mode and enter the name and, maybe the model. Most people use an object PLUS a text box which causes problems when you want to move objects around the page.

Quick Aside – textbox or object property

Most people would draw a line, then get the text tool to “add text” to the line.

But later on, if you need to move the VLAN around the page, the text gets left behind…..

The best way around this is to double click the VLAN graphic and get a text box. This text ‘belongs‘ to the ‘line’ so when you move the line, it always keeps the information.

I cover this topic in a lot more detail in THIS POST including some useful formatting tips for .

Labels – where do I the labels ?

A diagram is a picture with information on it. It’s not art. But when I put labels on the interfaces, the diagram start to look crowded.

The information could be split into two parts, the VLAN and the interface details. Lets try that again. This time with a bit of colour as well.

What is not very clear, is which lines connect to which. You can tell by where they end, but in much larger diagrams, its not so clear. Lets use the line ends to show the connection. Note: you should mark only one end. Since it is nearly always the ‘wrong’ end that gets the marker you can either rotate the line, choose the other end.

Now, this is a lot nicer looking.

Noting the different types of diagrams and their complexity

Some people don’t have the opportunity to draw big or complicated networks. I find this approach works well for large diagrams that have a lot of network elements and you want to capture the details of the device, which VLAN they connect to, and the interface addresses. ((In fact, I am not generally a believer in this kind of documentation. Trying to keep this documentation up to date, and accurate, requires will power that very few people have.

Design Diagrams are different

Its worth noting that I would not create this type of diagrams when I am designing. A design diagram for this network contains a lot less information and more accurately represent the ‘approach’ or the ‘intent’ of the design.

For example, the high level design for the diagram above would look something like this, where the design intent that all elements are redundant is not clear from looking at the diagram, but anyone reviewing the design would understand the functional intent.

Wrap Up

So the overview here is for implementation diagrams that are likely to be used by field or operations people. The great failing of this documentation is that operational people do not update these diagrams unless driven to it by management.

Still, these are some suggestions on how to do it.

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