Network Design Templates

Templates form the basis for network design and engineering, particularly for offices and data centers. Templates describe how a site (or data center or part of the data center) should be configured. Templates should, at a minimum, cover:

- 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.

These templates can then be used to engineer actual network designs. Adherence to all aspects of the templates should be a primary goal while engineering and configuring a network. While deviation is understandable based on specific needs, it should only be allowed on exception. This drives standardization and homogeneity through the network, increasing stability and simplifying network support.

Now, using templates does remove a lot of the creative design aspects of network engineering. However, this is a human issue, not a business problem. Networks should be built to efficiently serve the business. Having standard designs does that. Using the individual creative skills of each engineer, while making network engineers happy, leads to complex networks, raising support costs and lowering performance. Nonetheless, using the creative skills of each engineer can be done. Engineers should be involved in the template creation process. Templates will be different for each organization based on the requirements of that organization. This is where the engineers can add their creative skill - designing the templates. Make sure your network engineers are involved in the template creation process. This will ensure there is support for actually using the templates to build sites since the engineers had a part in their creation.

Finally, templates need to be built using standard documentation formats (building standards with standards). The templates need to look the same so they can be easily understood. So, before doing the actual designs for the templates, decide how the templates will look. Pick the format, come up with a documentation template, and use icons that everyone agrees on. Icons are particularly important. Every engineer has his or her favorite icon to represent a router. Some like the light-blue Cisco icons; others like the dark blue ones; for a while I wanted to just use circles. Pick icons everyone will use and agree on, then make those the standard icons. Build your templates using those agreed-upon icons.

Here is an example of the "Logical Design" page from a medium size site template:

Notice the diagram uses a documentation template which has fields for the "Title", "Project", "Author", etc.

These fields help track information about the template and make the design more professional. The icons are also standardized with an icon legend as part of the document.

The complete template includes the sections noted above: High-level, Physical, Logical, and Routing.

When an engineer needs to build an actual site, he can take this template, change the variable information (for example, IP addressing), and complete the design. Now the site is designed to a standard and is ready to be implemented. Furthermore, the site documentation is also done. It is simply the template with site specific information.