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CCNA Interview Questions in Kolkata

36 practice questions with answers for CCNA interviews in Kolkata.

CCNA jobs in Kolkata

Kolkata has a steady IT-services and BFSI technology job market around Salt Lake Sector V and New Town. Many openings are with service companies and their delivery centres, with a focus on strong fundamentals.

Below are 36 questions that match the mix of service, product and domain employers hiring network support engineers in Kolkata.

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01

A new VLAN's users do not get DHCP addresses, but other VLANs work. What do you check?

IP ServicesMedium
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I check that the SVI for the new VLAN is up and has ip helper-address pointing to the DHCP server, that the server has a scope for that subnet with the right gateway, and that the scope is activated. I confirm the VLAN is allowed on trunks. If DHCP snooping is enabled, I check the uplink is trusted, otherwise offers from the server are dropped.
02

What is the difference between a hub, a switch and a router?

Network FundamentalsEasy
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A hub is a Layer 1 repeater: it floods every bit out of every port, so all ports share one collision domain. A switch is Layer 2: it learns MAC addresses and forwards frames only to the correct port, giving each port its own collision domain. A router is Layer 3: it forwards packets between IP networks and separates broadcast domains.
03

Why is Spanning Tree Protocol needed?

STP and EtherChannelEasy
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Redundant Layer 2 links create loops, and Ethernet frames have no TTL, so broadcasts circulate forever, causing broadcast storms, MAC table instability and duplicate frames. STP (802.1D) blocks redundant paths so there is one loop-free path to every switch, and unblocks a backup link if the active one fails. Without it, a single loop can take down a whole campus within seconds.
04

Two OSPF routers are directly connected but show no neighbour at all. How do you troubleshoot?

Routing and OSPFMedium
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I check that the interfaces are up and in the same subnet, then show ip ospf interface to compare area, hello and dead timers, network type and authentication. I make sure the interface is not passive and that the network statement or ip ospf area command covers it. Finally I check that no ACL blocks protocol 89 or multicast 224.0.0.5, and use debug ip ospf adj if needed.
05

Explain the main IPv6 address types.

IP Addressing and SubnettingMedium
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Global unicast (2000::/3) is publicly routable. Unique local (fc00::/7, in practice fd00::/8) is like private IPv4. Link-local (fe80::/10) is auto-created on every IPv6 interface and used for neighbour discovery and routing next hops. Multicast is ff00::/8, for example ff02::1 all nodes and ff02::2 all routers. Anycast is a unicast address shared by several devices. IPv6 has no broadcast.
06

What is the difference between autonomous APs, controller-based APs and cloud-managed APs?

Wireless and AutomationMedium
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Autonomous APs are configured one by one and suit very small sites. Lightweight APs are managed by a Wireless LAN Controller using CAPWAP tunnels, which centralises configuration, RF management and roaming, and suits campuses. Cloud-managed APs are configured from a cloud dashboard, ideal for many branches. Split-MAC means real-time functions stay on the AP while management sits on the controller.
07

A PC in VLAN 20 cannot reach a PC in VLAN 30. What do you check?

Switching and VLANsMedium
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First I check each PC has the correct IP, mask and gateway for its VLAN. Then I confirm the switch ports are in the right VLANs with show vlan brief, and that the trunk to the Layer 3 device allows both VLANs using show interfaces trunk. On the Layer 3 device I check the SVIs or subinterfaces are up and have the right IPs, and that no ACL blocks the traffic.
08

What is a REST API and which HTTP methods map to CRUD?

Wireless and AutomationEasy
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A REST API exposes resources at URLs and is stateless, usually with JSON payloads over HTTPS. CRUD maps to HTTP verbs: POST creates, GET reads, PUT replaces or PATCH partly updates, and DELETE removes. Responses use status codes such as 200 OK, 201 Created, 401 Unauthorized, 404 Not Found and 500 Server Error. Controllers expose northbound REST APIs for automation.
09

What are DSCP and CoS markings?

IP ServicesHard
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CoS is a 3-bit priority field in the 802.1Q tag, values 0 to 7, used only on Layer 2 trunks. DSCP is a 6-bit field in the IP header, values 0 to 63, which survives across routed hops. Common values: EF (46) for voice, AF41 (34) for video, CS3 (24) for call signalling and default (0) for best effort. Mark close to the source and trust markings only at controlled boundaries.
10

A user complains the network is slow and the switch port shows many late collisions and CRC errors. What do you check?

Network FundamentalsMedium
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Late collisions usually mean a duplex mismatch, and CRC errors point to bad cabling or interference. I would run show interfaces on the port to see duplex, speed and error counters, check the PC NIC settings, and set both sides to auto or hard-code both identically. Then I would replace the patch cable, clear counters and watch whether errors still increase.
11

What are the first hop redundancy protocols and how does HSRP work?

Routing and OSPFMedium
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FHRPs give hosts a virtual gateway IP shared by two or more routers. HSRP is proprietary: routers elect an active router by highest priority (default 100), and the standby takes over the virtual IP and MAC if hellos stop. Preempt lets a higher priority router reclaim the role. VRRP is the open standard, and GLBP adds load sharing across several routers.
12

How do you configure inter-VLAN routing on a Layer 3 switch with SVIs?

Switching and VLANsMedium
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Enable routing and create an SVI per VLAN as the gateway. ip routing interface vlan 10 ip address 192.168.10.1 255.255.255.0 ip helper-address 10.0.0.50 no shutdown interface vlan 20 ip address 192.168.20.1 255.255.255.0 no shutdown show ip route connected
13

How do you use CDP and LLDP to discover neighbours?

Network FundamentalsMedium
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CDP is a proprietary Layer 2 discovery protocol enabled by default on IOS; LLDP is the open IEEE 802.1AB standard. show cdp neighbors show cdp neighbors detail configure terminal lldp run show lldp neighbors detail Detail output shows the neighbour's IP, platform and port. Disable CDP on internet-facing ports with no cdp enable.
14

Tell me about a time you found a security issue and reported it.

Network SecurityMedium
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Situation: during a routine audit I noticed SNMP v2c with the default community public on several access switches. Task: close the gap without disrupting monitoring. Action: I reported it to my lead with evidence, proposed SNMPv3 with an ACL, tested with the monitoring team and rolled out in two batches. Result: the risk was closed in a week and SNMP checks were added to our device baseline.
15

Describe a time you disagreed with a senior engineer about a network design. How did you handle it?

Routing and OSPFMedium
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Situation: a senior engineer wanted static routes for twelve new branches. Task: I believed OSPF would scale better. Action: instead of arguing in the meeting, I built both options in a lab, measured failover time and listed the change effort for each. I shared the results privately first. Result: we agreed on OSPF with summarization at the hub, and he asked me to write the standard. I learned that data persuades better than opinions.
16

A host shows IP 169.254.12.5. What does this mean and what will you check?

IP Addressing and SubnettingEasy
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169.254.x.x is an APIPA address, assigned when the host fails to get a DHCP lease. I would check that the port is up and in the correct VLAN, that the DHCP server has free addresses in the scope, and that the router interface for that VLAN has ip helper-address pointing to the server if the server is remote. Then I run ipconfig /renew and check server logs.
17

How do you quickly calculate how many subnets and hosts a mask gives?

IP Addressing and SubnettingMedium
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Use two formulas and memorise the mask octets. Subnets = 2^(borrowed bits) Hosts = 2^(host bits) - 2 Example: 10.0.0.0/8 to /20 -> 2^12 = 4096 subnets, 2^12 - 2 = 4094 hosts Mask octets: 128 192 224 240 248 252 254 255 Block size = 256 - mask octet
18

What is 802.1Q tagging?

Switching and VLANsEasy
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802.1Q inserts a 4-byte tag after the source MAC in the Ethernet frame. The tag holds a 12-bit VLAN ID (1 to 4094 usable), 3 priority bits used by CoS for QoS, and a DEI bit. The tag is added when a frame leaves a trunk and removed at an access port. Older ISL encapsulation is obsolete; modern switches support only 802.1Q.
19

What are the key elements of a security program for a network?

Network SecurityEasy
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A security program combines user awareness training, physical access control, and technical controls such as strong authentication, firewalls, IPS, VPNs and patching. It is built around the CIA triad: confidentiality, integrity and availability. Policies define what is allowed, and logging and monitoring detect problems. CCNA focuses on device hardening, ACLs, Layer 2 security, AAA, VPNs and wireless security.
20

How does a switch learn and forward frames?

Network FundamentalsMedium
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A switch reads the source MAC of each incoming frame and records it with the port in the MAC address table. For forwarding it looks up the destination MAC: a known unicast goes out one port, while unknown unicast, broadcast and most multicast frames are flooded in the VLAN. Entries age out after 300 seconds by default. Check with show mac address-table.
21

Your company is running out of IP addresses on a /24 user subnet. What options do you have?

IP Addressing and SubnettingMedium
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Options: expand to a /23 if the adjacent block is free and update the router and DHCP scope; create a new VLAN and subnet for some users, which also limits broadcast size; shorten DHCP lease times if many guest devices hold leases; and move printers, phones and IoT devices to their own subnets. Long term, plan an addressing scheme with growth headroom and consider dual-stack IPv6.
22

Which commands would you use to test end-to-end reachability and find where packets stop?

Network FundamentalsMedium
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ping tests reachability and round-trip time, and traceroute shows each Layer 3 hop. R1# ping 10.2.2.2 source Loopback0 R1# traceroute 10.2.2.2 PC> tracert 10.2.2.2 An extended ping lets you set source, size and the DF bit to test MTU. Where traceroute shows asterisks, that hop is dropping or filtering ICMP.
23

How are ACL entries processed and what is the implicit deny?

Network SecurityEasy
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ACL entries are checked top-down and the first match decides permit or deny; later lines are ignored. Every ACL ends with an invisible deny any, so traffic that matches no line is dropped. Therefore specific entries must come before general ones, and an ACL with only deny statements blocks everything. Always add a permit for allowed traffic and test after applying.
24

What is EtherChannel and its benefits?

STP and EtherChannelEasy
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EtherChannel bundles 2 to 8 physical links into one logical port-channel. STP sees it as one link, so all members forward instead of one being blocked. It adds bandwidth and redundancy, as one member failing does not drop the channel. Traffic is load-balanced per flow using a hash of MAC, IP or port fields, so a single flow still uses only one member link.
25

Compare single-mode and multimode fiber.

Network FundamentalsMedium
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Single-mode fiber has a small core (about 9 microns) and uses a laser, so it carries light over long distances, often 10 km or more. Multimode fiber has a larger core (50 or 62.5 microns), uses cheaper LED or VCSEL optics and suits shorter runs inside a building or data center, usually up to a few hundred metres at 10 Gbps. SFP modules must match the fiber type.
26

After adding a new VLAN, users on one access switch cannot use it but others can. Why?

Switching and VLANsMedium
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The most likely cause is the trunk to that switch does not allow the new VLAN, because someone configured an explicit allowed list. Check show interfaces trunk and add it with switchport trunk allowed vlan add 50, not without add, which would replace the list. Also confirm the VLAN exists on that switch with show vlan brief, especially if VTP is transparent.
27

What must match for an EtherChannel to form?

STP and EtherChannelMedium
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Member interfaces must have the same speed and duplex, the same mode (access or trunk), the same access VLAN or the same native and allowed VLAN list on trunks, and compatible negotiation modes. Mismatched settings put members into suspended state. Configure settings on the port-channel interface so they are pushed to members, and verify with show etherchannel summary.
28

Users complain Wi-Fi is slow in a conference room with 60 people. What do you check and fix?

Wireless and AutomationMedium
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This is usually a capacity, not a coverage, issue. I check client count per AP and channel utilisation on the controller. Fixes include adding APs with lower transmit power, steering clients to 5 or 6 GHz with band steering, disabling low data rates such as 1, 2 and 5.5 Mbps, using 20 or 40 MHz channels in dense areas, and limiting per-client bandwidth on the SSID.
29

Tell me about a time you led a network migration or a major change.

Network FundamentalsHard
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Situation: our office had to move 300 users from old access switches to a new stack in one weekend. Task: I owned the plan. Action: I documented every port, pre-built configs, ran a pilot on one floor, wrote a rollback plan and kept a call bridge open with the desktop team. Result: we finished two hours early with only three port issues, fixed on Monday morning. I learned that a tested rollback plan gives the whole team confidence.
30

What is Root Guard and Loop Guard?

STP and EtherChannelHard
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Root Guard on a designated port puts it into root-inconsistent state if a superior BPDU arrives, protecting the planned root bridge, so it is used on distribution ports facing access switches. Loop Guard stops a non-designated port from becoming designated when BPDUs stop arriving, such as with a unidirectional fiber fault. UDLD complements Loop Guard by detecting one-way links.
31

What is port security and what are its violation modes?

Network SecurityMedium
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Port security limits the MAC addresses allowed on an access port, either statically or by sticky learning. If an extra MAC appears, the violation mode acts: shutdown (default) err-disables the port, restrict drops the frames, logs and increments a counter, and protect silently drops frames. It stops MAC flooding and unauthorised devices on user ports.
32

Users behind a router can reach local servers but not the internet after a firewall change. NAT is configured. What do you check?

IP ServicesMedium
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I check show ip nat translations to see whether translations appear when users browse. If none, I verify ip nat inside and ip nat outside on the correct interfaces, that the ACL used by NAT matches the user subnets, and that the overload interface has an IP. I also check the default route and run show ip nat statistics for hits and misses.
33

How do you configure PAT (NAT overload)?

IP ServicesMedium
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Mark interfaces, match inside hosts with an ACL and overload the outside interface. interface GigabitEthernet0/1 ip nat inside interface GigabitEthernet0/0 ip nat outside access-list 1 permit 192.168.0.0 0.0.255.255 ip nat inside source list 1 interface GigabitEthernet0/0 overload show ip nat translations
34

Two hosts are in the same VLAN but one has mask /24 and the other /25. What problems may occur?

IP Addressing and SubnettingMedium
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Each host decides local or remote using its own mask. With 192.168.1.10/24 and 192.168.1.200/25, the first thinks .200 is local and ARPs directly, but the second sees .10 as remote and sends replies to its gateway. Traffic can become one-way or asymmetric and may break completely if the gateway does not route it back. Fix the mask so both match the design.
35

What is an underlay and an overlay network?

Wireless and AutomationHard
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The underlay is the physical IP network of switches and routers that provides basic reachability, for example OSPF or IS-IS on routed links. The overlay is a virtual network built on top using tunnels such as VXLAN, so logical segments can stretch across the fabric independent of physical topology. SD-Access and SD-WAN use this model, with a fabric controlling the overlay.
36

How do you handle pressure when an outage affects many users?

IP ServicesEasy
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Situation: DHCP failed for 300 users at 9 a.m. on a Monday. Task: restore service while keeping managers updated. Action: I stayed calm, followed the bottom-up method, found the DHCP server's scope was full after a lease time change, extended the scope and shortened leases. I sent updates every 15 minutes. Result: users were back in 30 minutes, and we added scope utilisation alerts to monitoring.

Companies with offices in Kolkata (4)

IT services

Wipro

CCNA interview questions

  • 30 questions
  • 4 rounds

Bengaluru, Hyderabad, Pune +2

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IT services

Cognizant

CCNA interview questions

  • 30 questions
  • 4 rounds

Chennai, Bengaluru, Pune +2

View questions
IT services

IBM

CCNA interview questions

  • 30 questions
  • 4 rounds

Bengaluru, Pune, Hyderabad +2

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Telecom

Ericsson

CCNA interview questions

  • 30 questions
  • 4 rounds

Gurugram, Bengaluru, Chennai +2

View questions

Frequently asked questions

Which companies hire CCNA professionals in Kolkata?

Companies with large offices in Kolkata include Wipro, Cognizant, IBM, Ericsson. Use their company pages below to practise employer-specific sets.

Are CCNA interviews in Kolkata different from other cities?

The questions depend more on the company than the city. Kolkata's mix of employers decides the style: Many openings are with service companies and their delivery centres, with a focus on strong fundamentals

How do I find CCNA jobs in Kolkata?

Shortlist companies with Kolkata offices, keep your CV focused on CCNA projects, apply on company career pages and job portals with the Kolkata filter, and practise the questions on this page before each interview.

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