Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2ArchitectureHard
A network engineer is designing a highly available and scalable network for a new campus building. The design specifies a collapsed core architecture that must support both wired and wireless clients, provide consistent policy enforcement, and minimize latency. Which combination of network design principles and technologies would be most appropriate for the core and distribution layers in this scenario?
- AThree-tier design with redundant links and VRRP
- BCollapsed core with Layer 2 access, EIGRP, and HSRP
- CCollapsed core with Layer 3 access, OSPF, and ECMP
- DHierarchical design with Spanning Tree Protocol and static routing
Show answer & explanationAnswer & explanation
Correct answer: C. Collapsed core with Layer 3 access, OSPF, and ECMP
A collapsed core architecture combines the core and distribution layers, reducing latency. Implementing Layer 3 at the access layer (routed access) eliminates STP complexities, provides faster convergence, and allows for efficient routing protocols like OSPF with Equal-Cost Multi-Path (ECMP) for load balancing and redundancy, which aligns with high availability, scalability, and minimized latency requirements.
Why the other options are wrong
- A. Three-tier design adds more latency due to additional hops; VRRP is a first-hop redundancy protocol, but a full Layer 3 design with ECMP is more efficient for load balancing.
- B. Layer 2 access with HSRP is common but can introduce STP issues and doesn't fully leverage Layer 3 advantages for scalability and load balancing at the access layer.
- D. Hierarchical with STP and static routing is less scalable and has slower convergence compared to modern designs, not ideal for high availability/scalability.
Routed Access (Layer 3 Access)
A campus network design where access switches perform Layer 3 routing, extending the routing domain to the access layer and eliminating the need for Spanning Tree Protocol.
- Eliminates STP complexity and convergence issues.
- Enables faster convergence and more efficient routing.
- Facilitates Equal-Cost Multi-Path (ECMP) for load balancing.
Memory trick: Layer 3 to the access is 'faster, simpler, stronger'.