Logical Network Diagrams

Date July 3, 2008

As I've often mentioned, network documentation shall set you free. It enables monitoring, it clarifies murky or misunderstood concepts, and it lends itself to allowing improvement of the infrastructure.

Ideally, documentation should be the first step of the building process. Architects don't get a bunch of lumber and throw it around until it looks cool, then draw blueprints. They plan first, and so should you.

I'm nearing the end of a build process for my stack of hardware that's going into a colocation in NJ. In terms of network diagrams, I've gone from back-of-the-napkin drawings of clouds to fully realized diagrams created in OmniGraffle (a very, very cool diagramming program if you use Mac).

Here's what the logical network at the colocation will look like:

Network Diagram

As you might have noticed, the only thing that isn't symmetrical is the Brocade fibre-channel switch. That's because they're several thousand dollars. I tried to get the budget for it, but it was no go. I'm still looking for a cheaper solution that doesn't involve a single failure point.

Anyway, as you can see, this diagram can help me understand at a glance where any specific piece of hardware fits in the scheme. There are lots of other ways to diagram the same thing. For (a lot) more information, check this great link: http://www.networkdocumentation.com/.

  • John Doe

    Your networkplan is usable in very small enviroments.

    Try to document 500+ Server, serveral hundred switches and the like.

    Not as easy as you might think. :)


  • Matt


    I'm sure! Most people have never been in the position to have to catalog that many assets.

    What tools do you use for that? How do you create logical diagrams of that magnitude?

  • Joe

    While the icons from Visio or other programs are useful, I've found using simple rectangles for devices to be much more useful. If you try to label and detail icons, you have a bunch of text all over the diagram. However, if you type details of the device in a generic rectangle, you can have a more useful diagram. You can list device type, vendor, os version, hostname, ip address, interfaces, vlans. To differentiate between devices, you could adjust the shade color or the rectangle. Give it a try, you may never go back to using icons.

  • Matt


    That's a really great idea for viewing information. Do you ever have issues identifying certain devices, such as routers from firewalls, when looking at the "big picture"?

  • http://Cyberi.US Bob Montgomery

    If you're truly a borderline zealot for technical diagrams, I've found a tool called yEd from yWorks can be adapted for mixed hierarchical-network diagrams of complex internetworked components. Drawings of the type, say, one encounters when mapping configurations of thousands of processors, FC/IB/GbE switches, RAID controllers, and the like down to the connector/FRU level of detail. The cool thing about yEd is it's ability to expand/collapse hierarchy elements which themselves may be connected to other elements in other hierarchies, and automagically allow one to move about connected elements while the program handles all the redrawing details, without worrying about drawing artifacts like page boundaries impeding interactive fluidity - CAD instead of PPT/Visio slideware. The perfect thing for illustrating which e.g. end-to-end IB cable IDs associated with specific ports on IB adapters in I/O tray assemblies within expansion bays between multiple chassis. Kinda short in the pretty icon department - you'll have to provide your own, and when it comes to plotting the whole diagram out, font scaling is often a problem across deep hierarchies.