CCNA Data Center Interview Questions: What to Study Now That the Exam Is Retired

Key takeaways

• CCNA Data Center no longer exists. The topics live on in CCNA 200-301 and the CCNP Data Center track, so prepare for the skills, not the retired exam name.
• Expect fundamentals first (VLANs, trunks, STP, ACLs), then data-centre design (vPC, spine-leaf, VXLAN), then storage and virtualisation.
• Troubleshooting questions test your method. Answer bottom up and say out loud what you check at each layer.
• If a question touches a platform feature you have not used, say so, then explain the concept. That is better than guessing commands.

Is CCNA Data Center still a certification?

No. Cisco retired the CCNA Data Center certification, along with CCNA Security, Voice, Wireless, Routing and Switching, in February 2020 and replaced them with a single CCNA (200-301). Data centre content moved to the professional level, under the CCNP Data Center track. If a job post still says CCNA Data Center, it is usually an old template. Ask the recruiter what the team actually runs: Nexus, ACI, VMware, storage arrays.

Check Cisco's current certification pages before choosing an exam, because track names and exam codes change.

How to use this list

Read each answer, then say it in your own words without looking. Then build the small lab it describes, even on virtual images. Memorised answers collapse after the first follow-up question. If you have not yet covered the basics, start with the CCNA 200-301 course.

Fundamentals

1. What are the main parts of a data centre?

Compute (servers), storage, networking, power (utility feed, UPS, generators), cooling, physical security and the management systems that monitor all of it. Interviewers want you to show that the network is only one piece and depends on the others.

2. What is the difference between a Layer 2 and a Layer 3 switch?

A Layer 2 switch forwards frames by MAC address inside a VLAN. A Layer 3 switch also routes packets between VLANs and subnets by IP address, using SVIs or routed ports. In a data centre, Layer 3 switches usually form the aggregation or leaf layer.

3. What is a VLAN and why is it used in a data centre?

A VLAN splits one physical switch network into separate broadcast domains. It isolates management, storage, backup and application traffic, reduces broadcast load and limits how far a problem spreads. Traffic between VLANs must pass through a router or Layer 3 switch.

4. What is a trunk and what does 802.1Q do?

A trunk carries many VLANs over one link. 802.1Q adds a 4-byte tag to each frame with the VLAN ID, and the native VLAN travels untagged. A mismatched native VLAN is a classic cause of strange behaviour and CDP or STP warnings.

5. What does Spanning Tree Protocol do, and why is it a problem in data centres?

STP stops Layer 2 loops by blocking redundant links. The cost is that half your uplinks sit idle, and convergence after a change can disrupt traffic. That is why data centres moved to vPC or multi-chassis designs and, in newer fabrics, routed Layer 3 designs.

6. How does a load balancer work?

It presents a virtual IP to clients and spreads requests across a pool of servers, using methods such as round robin, least connections or hashing. It runs health checks and removes a failed server from rotation. Many also terminate TLS and keep session persistence.

7. What is the difference between DAS, NAS and SAN?

DAS is storage attached directly to one server. NAS shares files over the network, using NFS or SMB. A SAN gives servers block-level storage over a dedicated network, using Fibre Channel or iSCSI. The server sees a SAN volume as a local disk.

Data centre networking and Nexus

1. What is a vPC on Cisco Nexus switches?

A virtual PortChannel lets two Nexus switches appear as one logical switch to a downstream device, so the device can bundle links to both with one port channel. It removes blocked STP links and keeps working if one switch fails. It needs a peer link and a keepalive link between the pair.

2. What is a FEX?

A Fabric Extender is a remote line-card-like device that adds many host ports and is managed from its parent Nexus switch. It cuts management work and cabling to the core, but it has no local intelligence, so all traffic goes up to the parent.

3. What is spine-leaf architecture?

Every leaf switch connects to every spine switch, and servers connect only to leaves. Any server is the same small number of hops from any other, so latency is predictable and bandwidth scales by adding spines. It suits the east-west traffic that dominates modern data centres.

4. What problem does VXLAN solve?

VLAN IDs run out at 4094, and Layer 2 domains are hard to stretch over routed networks. VXLAN wraps Layer 2 frames in UDP and uses a 24-bit segment ID, allowing about 16 million segments over a Layer 3 underlay. BGP EVPN is commonly used as its control plane.

5. What is Cisco ACI in one paragraph?

Application Centric Infrastructure is Cisco's policy-driven data centre fabric. An APIC controller defines tenants, endpoint groups and contracts, and the spine-leaf fabric enforces them. You describe what may talk to what, and the controller programs the switches. Know it at concept level for a CCNA-level interview.

6. What is the purpose of network segmentation?

It limits the blast radius of an attack or fault, improves performance by cutting broadcast domains, and lets you apply different policy to each zone. In a data centre it appears as VLANs, VRFs, firewall zones or ACI endpoint groups.

7. How would you write an ACL to allow one subnet to reach a server VLAN?

Use an extended ACL and apply it close to the source or the destination as policy requires. Always remember the implicit deny at the end, and that ACLs are read top to bottom.

ip access-list extended APP-IN
 permit tcp 192.168.1.0 0.0.0.255 any eq 443
 deny ip any any log
interface Vlan10
 ip access-group APP-IN in

8. How do you configure QoS for voice?

Classify voice by DSCP EF, put it in a priority queue and police it so it cannot starve other traffic.

class-map match-all VOICE
 match dscp ef
policy-map QOS-OUT
 class VOICE
 priority 1000
interface GigabitEthernet0/1
 service-policy output QOS-OUT

Storage and virtualisation

1. What is a hypervisor, and what are the two types?

A hypervisor creates and runs virtual machines. Type 1 runs directly on hardware, for example VMware ESXi or Microsoft Hyper-V. Type 2 runs on top of an operating system, for example VirtualBox or VMware Workstation. Data centres use Type 1.

2. How does server virtualisation change the network?

Many virtual machines share one physical NIC, so the access layer becomes a virtual switch inside the host. VLAN trunks must reach each host, VMs can move between hosts with vMotion or live migration, and the network must keep the same VLANs and policy wherever the VM lands.

3. What is Fibre Channel zoning?

Zoning controls which initiators (servers) can see which targets (storage ports) on a Fibre Channel fabric. It works like an access list for storage. Single-initiator zoning, one server per zone, is a common good practice.

4. What is FCoE and what are its requirements?

Fibre Channel over Ethernet carries Fibre Channel frames over lossless Ethernet to cut cabling and adapters. It requires data centre bridging features such as priority flow control. It is less common in new builds than iSCSI or NVMe over fabrics.

5. What is iSCSI?

iSCSI carries SCSI block commands over TCP/IP, so you can build a SAN on ordinary Ethernet. Best practice is a dedicated VLAN or network, jumbo frames if the whole path supports them, and multipathing.

6. How would you design for high availability?

Remove single points of failure at every layer: dual power feeds, redundant switches and NICs, port channels or vPC, redundant storage paths, clustered or load-balanced applications, and tested failover. Say that untested failover does not count.

Operations, recovery and troubleshooting

1. What is a data centre interconnect (DCI)?

A DCI links sites for replication, disaster recovery and workload mobility. Options include dark fibre, DWDM, MPLS or VXLAN-based stretch designs. The key trade-offs are latency, bandwidth and how much Layer 2 you stretch, since stretching it also stretches failures.

2. How do you plan disaster recovery?

Set RPO (how much data loss is tolerable) and RTO (how long recovery may take) with the business. Then choose backup, replication and failover to meet them, document runbooks and test them on a schedule.

3. What is hot aisle and cold aisle containment?

Racks face each other so cold air enters at the front of servers from one aisle and hot air exhausts into the other. Containing the aisles stops the two mixing and improves cooling efficiency.

4. What does DCIM software do?

Data Center Infrastructure Management tools track power use, cooling, space, assets and environmental sensors, so capacity can be planned and faults found early.

5. A server cannot reach its gateway. What do you check first?

Work bottom up. Check the link light and interface status, then the VLAN and access or trunk configuration, then the MAC address table and ARP, then the gateway SVI and any ACL. Describe the order out loud. Interviewers score the method as much as the answer.

6. Users report slow access to an application. How do you narrow it down?

Define the scope: one user, one site or everyone. Compare latency and loss, check interface errors, utilisation and queue drops, then look at the server and database. Do not assume it is the network until counters show it.

How to answer well

• Start with a one-sentence definition, then give one example from a lab or project you have actually done.
• Draw. A quick sketch of a vPC pair or spine-leaf fabric on paper shows you understand the topology.
• Know the numbers that matter: 4094 usable VLANs, 24-bit VXLAN IDs, the order of an ACL, and what RPO and RTO mean.
• Be straight about limits. Saying "I used it in a lab but not in production" is respected.

Next steps

Build the fundamentals first with the CCNA 200-301 course, then look at virtualisation interview questions and cloud infrastructure interview questions for the other half of a data centre role.

Related reading

• [2026] CCNA Interview Questions on ACLs
• [2026] CCNA Interview Questions and Answers
• [2026] CCNA Interview Questions on VLANs