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:

.

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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