Describing the configuration problem
Several production networks out there have their configuration applied to network devices without any additional external definition. Some of them have network diagrams describing the network, but the majority have outdated or incomplete diagrams. Therefore, in most cases, you might need to read running device configurations to understand the details of the network operation.
In some network providers, diagrams are used for an initial understanding of the network or as an overall overview. Once the engineers have enough confidence in their network, the diagrams are just ignored or not used anymore. Some would update their diagrams, but for most engineers, this task is not a priority and usually is left behind.
It is also common for some engineers to apply configuration fixes directly into production devices to solve catastrophic or urgent failures. In other cases, additional configuration is applied temporarily for troubleshooting, but never...
