The collapsed core architecture and the three-tier architecture are design approaches, not physical separations. It’s a way of thinking about the network, not a way of viewing actual network devices.
- Collapsed core
- Core and Distribution layers are combined as a single layer
- The collapsed core devices must be capable of core functions: high speed network connectivity and distribution functions: routing, filtering, NAT, etc.
- Three-tier is a hierarchical model:
- Core - move large amounts of traffic as fast as possible. Majority of users
- Distribution - routing, filtering, WAN access, NAT, firewalls, redistribution
- Access - device connectivity
- Three separate levels doesn’t necessarily mean three separate physical devices