Layer-0 Page for Network Design Templates

Adds Another Page in Addition to the Standard Four Pages

The third blog on wrote on Network World's Cisco Subnet was about Network Design Templates. Proper Network Design Templates are one of the pillars of a written network architecture. If you work on a network engineering and architecture team, Network Design Templates should be seen as your product line. If you are truly an engineer, then your job is to build product specifications that a manufacturing unit (network implementation team) can build to. That is what Network Design Templates are. They are your product line. They take raw materials (routers, switches, cables, routing protocols, etc) and describe how to put them together into a synergistic product that adds value. Someone else may actually build the network, but it will be based on your design. And let's be honest, the people designing the product are always more valuable to a company than the people putting it together.

An interesting note about my original Network Design Templates blog. I get a weekly page hit report from Network World. Usually the blog I write the week before has the highest hit count (obviously). But Network Design Templates is always in the top 5, if not 3rd most popular. Last week it was #4 most popular. There's definitely a consistent demand for the information on that page.

Recently, we looked at our existing standard for Network Design Templates:

  • High Level Design - as a summary, how this part of the network connects to the broader network.
  • Physical Design - which network devices to use, how the network devices are cabled, what physical ports are used, racking, and power.
  • Logical Design - Layer2/3 design for network equipment (VLANs, IP Addressing).
  • Layer-3 Routing - how routing protocols (statics, IGPs, BGP) are used in the design.

and decided we needed to add another page. In this case we broke out the racking and power specifications from the Physical Design page, creating a separate page called "Layer-0" design. We needed something that was clearly different from "Physical Design" which could certainly also include rack and power specifications, so we called it "Layer-0". There is a bunch of good information to include in the Layer-0 diagram; enough information that it can complicate the actual "Physical Design" page of the template which focuses on network physical information (Layer-1). Thus, there is a need for a separate Layer-0 page in the template. For example, proper PDU connectivity for each device can make a difference when dealing with different power phases. Using the wrong port on a managed-UPS could be disastrous in the future (I would hate to SSH into a managed PDU and power-cycle the wrong power port). This is all key information that adds to initial setup and the resiliency of the design while in operations. Racking information can also be provided. This is especially useful at remote field offices to ensure all devices are racked the same way. This makes troubleshooting simpler when you're trying to explain to that brand new CCNA which devices he should put the extra memory in. If wan-router-1 is always at the top of the rack, it's much easier. Layer-0 diagrams are a good addition to your existing Network Design Templates.

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