CDCP Network Infrastructure and Connectivity 4 — Questions and Answers
Question 1: Which spanning tree protocol variant provides the fastest convergence time in a data center switching environment?
- STP (802.1D)
- RSTP (802.1w) (Correct answer)
- MSTP (802.1s)
- PVST+
Correct answer: RSTP (802.1w)
RSTP (Rapid Spanning Tree Protocol) converges in seconds rather than the 30–50 seconds of classic STP, making it the fastest standard spanning tree variant.
Question 2: A data center uses ECMP (Equal-Cost Multi-Path) routing. What is the primary benefit of ECMP?
- Reduces the number of routing table entries
- Allows traffic load sharing across multiple equal-cost paths (Correct answer)
- Eliminates the need for a default gateway
- Provides automatic failover without reconfiguration
Correct answer: Allows traffic load sharing across multiple equal-cost paths
ECMP distributes traffic across multiple paths with the same routing metric, increasing aggregate bandwidth and providing redundancy.
Question 3: What is the purpose of a spine-and-leaf network topology in modern data centers?
- To reduce the total number of switches required
- To provide consistent low-latency east-west traffic between servers (Correct answer)
- To maximize north-south traffic throughput to the internet
- To eliminate the need for layer 3 routing within the data center
Correct answer: To provide consistent low-latency east-west traffic between servers
Spine-and-leaf topology ensures every leaf switch is exactly two hops from any other leaf, providing predictable, low-latency east-west traffic for server-to-server communication.
Question 4: Which protocol is used to aggregate multiple physical network links into a single logical link for increased bandwidth and redundancy?
- VRRP
- LACP (802.3ad) (Correct answer)
- OSPF
- MPLS
Correct answer: LACP (802.3ad)
LACP (Link Aggregation Control Protocol) per IEEE 802.3ad dynamically negotiates and manages link aggregation groups (LAGs) between switches and servers.
Question 5: In a data center context, what does 'oversubscription' mean in network design?
- Purchasing more bandwidth than needed from an ISP
- Having more downstream bandwidth capacity than upstream uplink capacity (Correct answer)
- Configuring more VLANs than a switch can support
- Using more IP addresses than the subnet allows
Correct answer: Having more downstream bandwidth capacity than upstream uplink capacity
Oversubscription is the ratio of total downstream port bandwidth to uplink bandwidth; a 4:1 ratio means four times more server-facing bandwidth than uplink capacity.
Question 6: Which network virtualization technology encapsulates layer 2 frames within UDP packets to extend VLANs across layer 3 networks in a data center?
- MPLS
- VXLAN (Correct answer)
- GRE
- 802.1Q trunking
Correct answer: VXLAN
VXLAN (Virtual Extensible LAN) encapsulates Ethernet frames in UDP/IP, allowing layer 2 segments to span across routed layer 3 networks and supporting up to 16 million segments.
Question 7: A data center network team wants to implement a first-hop redundancy protocol so servers always have an available default gateway. Which protocol is vendor-neutral and defined by an IEEE standard?
- HSRP
- VRRP (Correct answer)
- GLBP
- CARP
Correct answer: VRRP
VRRP (Virtual Router Redundancy Protocol) is the IEEE/IETF standard (RFC 5798) for first-hop redundancy, whereas HSRP and GLBP are Cisco-proprietary.
CDCP Network Infrastructure and Connectivity 4
Which spanning tree protocol variant provides the fastest convergence time in a data center switching environment?