IP Network Design Principles
The basic principles of good network design apply to all IGPs including IS-IS. The classic design methodology of layering the network into three main components (core, distribution, and access) needs to be applied as much as possible. The following sections discuss these three components.
The core is the network backbone and its primary function is to switch packets as fast as possible. As the core is the heart of the network, it must be redundant, reliable, and have full reachability to every destination in the network.
Because packet switching in the core must be fast, filtering and policy implementations in this part of the network must be limited and, if possible, avoided because, in general, these features ...