CCIE Network Design Flashcards

In the Cisco hierarchical network design model, which layer is responsible for routing between VLANs and applying QoS policies before traffic enters the core?

Answer: Distribution layer

The distribution layer aggregates access-layer traffic, performs inter-VLAN routing, and applies QoS and policy enforcement before handing off to the core.

Which design approach uses a single routing process to provide both intra-area fast convergence and scalability across multiple areas in OSPF?

Answer: Hierarchical OSPF with multiple areas

Hierarchical OSPF with multiple areas limits LSA flooding scope per area, enabling fast local convergence while backbone area 0 provides scalability across the domain.

A network designer is choosing between VSS and StackWise Virtual for a campus core. What is the primary design advantage of VSS/StackWise Virtual over traditional dual-chassis designs using HSRP?

Answer: Elimination of STP blocked ports by enabling active-active forwarding

VSS and StackWise Virtual create a single logical switch that allows both uplinks to forward traffic simultaneously, eliminating STP-blocked ports and doubling usable bandwidth.

When designing a WAN with diverse provider circuits for redundancy, which BGP attribute should be manipulated on inbound traffic to prefer one ISP over another without changing outbound path selection?

Answer: MED (MULTI_EXIT_DISC)

MED is advertised to neighboring ASes to suggest a preferred entry point into your AS, influencing how external providers forward traffic to you on inbound paths.

In a spine-leaf data center fabric design, what is the maximum number of hops between any two endpoints regardless of the fabric size?

Answer: 3 hops

In spine-leaf, any endpoint connects to a leaf, traffic crosses one spine, and reaches the destination leaf — always exactly 3 hops, ensuring consistent, predictable latency.

A designer needs to segment a campus network so that finance and HR traffic is isolated at Layer 3 without deploying separate physical switches. Which technology best satisfies this requirement?

Answer: VRF-Lite

VRF-Lite creates multiple independent routing tables on a single router or Layer 3 switch, providing complete Layer 3 isolation between departments without additional hardware.

Which design principle should be prioritized when sizing redundant power supplies and cooling in a network equipment room to meet 'five nines' (99.999%) availability?

Answer: 2N redundancy (fully duplicated systems)

2N redundancy provides a fully independent duplicate of every power and cooling component, ensuring no single failure — including entire PSU or cooling unit failure — causes downtime.