Best practices in network design

During this article we are going to touch most important aspects and building blocks considered as Best Practices in network design, which allow person to walk in and assess a situation by looking at network organization, then know and understand what he has, what he is going to do and how the network design will look like based on the best practices and at the same time satisfy the needs.
One fact that should be considered before going deep in this, that Network design is totally different than the network configuration. So we will touch here the technologies, best approaches to get a design satisfy your needs and be mature enough.

 

Lest us start with the recommended aspects and Best practices in network design:

Principle 1: Understand technology concepts

All the time we are focusing on the pure configuration for any technology or feature, so we  searched about how to configure OSPF, or how to setup bgp relationship between peers, how to configure load balancing over multiple links, and much more things; BUT this is not what you need for network design. You need actually to know and understand the concepts, what pieces go in the right puzzle spots, and know how things work/integrated together. So you need here to configure only when need it to know how it works, to test it, and to know the concept. The other point is know that it would work and do not guess or hope that it will work. So as summary consider the followings:

•  Configure when you need it (prove it).
• Understand and Know it (DON’T GUESS it will work , DON’T HOPE it will work) 

Principle 2: Simplify

There are many network designs work fine and have brilliant ideas, but at the same time are very complex and had many variables; that will lead the admins suffer when troubleshooting or when even a new enhancement/request appeared to be added to the network. So network design should be simple and easy to be expanded and enhanced.

So when designing IP subnetting of a network don’t complicate it or increase the number of subnets without actual needs for it. Same as for routing, it should be simple with minimum entries in the routing table rather than having too many routes from different routing protocols which are actually no needed.  At the end if you are a network designer and you need to use a technology within your network, it must be there for a need or solve a problem within your network, and not just to use this technology as is.

So let’s remember the followings:

•     Minimize IP address subnetting and use it whenever needed
•     Don’t add routes for the sake of routing
•     Distinguish between the “Best Practices” VS “Realistic design”
•     Build working and proven solution with cost effective approach

Principle 3: Build Your Templates

Important point to mention here is that no replacement for experience, so you may read hundreds of books and license of tens of lessons, but this will be as doing it by your hands and test the technology by yourself at your lab. Ultimately you need to build your template design that you can use them again and again, beside at the same time enhance them and tune them to be optimized. Another approach to consider is the usually used equipment, so you have to create your own catalogue of network equipment used, for example these are the switches I use, these are the routers I used, these are the access points I used, etc.

In summary:

•      Standardize your solution (VLANs design, IP Subnets design, BGP filter templates, Access list templates)
•      Suitable equipment to be used

Principle 4: Always Monitor

Always remember that when you setup a device in your design, build it to be monitored from outside and inside.  So you have to monitor and know whatever is happening within your network, firewall, servers, switches etc., and at the same time you have to monitor your network from the internet and how your network in being seen from outside, you can do it for example through SNMP with secure VPN. So visibility is so critical in your network design

So let’s remember the followings in this principle:

•       You must know how you will know about that
•       Visibility is Critical
•       Monitoring and alerting routine is critical

Principle 5: Documents. Keep it in your mind

You need to do it. Document. As initially nobody likes to do documents, but you can force yourself by just reserve a time for it, whenever you start preparing a network design, the best practice is to schedule a time frame for documentation. So whenever you reserve that time for documentation, do it even with handwritten notes or diagrams, because afterwards you will return back to them and produce a formal document. For sure documents will be needed during and after your network deign

So as summary note the followings:

•       Reserve a time for documentation
•       Handwritten notes better than no notes
•       Handwritten notes better than partial Visio diagram

So as summary we had touched the best practices in network design that any engineer should follow to have stable, simple, and flexible network which is satisfying the business requirements and maintain the security aspects. At the same time considering the monitoring and documentation part in addition to cost effectiveness in the design and equipment being used.