Network diagrams and documentation: Part 1

Network diagrams and documentation are the topics of this tip on keeping your network organized.

In today's enterprise environment, documenting the network is absolutely critical. The de facto standard tool for documenting networks is Microsoft's Visio, although several free, open-source alternatives exist.

In my experience, the vast majority of Visio network diagrams suffer from two problems: lack of information (or cluttered info), and confusion between logical and physical aspects of the network. Besides general laziness, the main reason for the lack of information is that there is quite a lot of information about networks worth keeping and when the network is large or complex, it can be a real challenge to fit the information onto a page. In this tip and the next, I want to explain a great way to accomplish that.

The first secret is Visio's "custom properties". Each stencil and object has them, and you can view them by selecting the "View" menu and then "Custom Properties Window". That should bring up a little dialog box with fields and values in it. When you click an item in your drawing, it will show you the values for that particular object.

Visio's stencils have default properties that include the following fields:
Manufacturer
Product Number
Part Number
Product Description
Asset Number
Serial Number
Location
Building
Room
Department

I've found those properties to be almost entirely useless. Fortunately, they're called "custom properties" for a reason. Right-click in the Custom Properties Window, or on the stencil or object itself, and you can add, remove or change fields to something more useful. If you change the stencil, then all future objects you create with that stencil will have your changes. If you change the object's properties, it affects only that object.

If you use Visio often to create network diagrams, I recommend you create a set of stencils with your own properties. Cisco has created some beautiful stencils to represent various equipment, and I chose a stencil to represent a regular switch (e.g. Cat2948G), a regular router (e.g. 2600), a layer 3 switch (e.g. 3550), a chassis-based switch (e.g. 6509), etc. Then I gave it the following custom properties:

Hostname
Make
Model
Contact
Mgmt Address

I also created stencils for each type of link in my networks, with a different color and width representing technologies such as Token-ring, Ethernet, Fast Ethernet, Gigabit Ethernet, ATM, and various WAN circuits. For the links, I assign the following custom properties as appropriate:

Device 1
Port number
IP Address
Device 2
Port number
IP Address
Speed
Duplex
VLAN number
Trunk Type
Circuit ID
and a general Description field.

There are a number of advantages to using this system. First, I keep a lot of information but I don't have to use 6-point font to fit it on the page. Second, and this is very important... when I print the diagram, only the basic boxes and lines show up. All of the IP addresses and other sensitive information is hidden. This means that I can hang diagrams on my office walls, or give copies to managers, customers or vendors without violating common-sense security practices.


Tom Lancaster, CCIE# 8829 CNX# 1105, is a consultant with 15 years experience in the networking industry, and co-author of several books on networking, most recently, CCSPTM: Secure PIX and Secure VPN Study Guide published by Sybex.


This was first published in April 2004

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