36 practice questions with answers for CCNA interviews in Coimbatore.
CCNA jobs in Coimbatore
Coimbatore has a growing IT-services and engineering-services market around TIDEL Park and its SEZs, supported by a large pool of engineering graduates. Many roles are with delivery centres of bigger IT firms.
Below are 36 questions that match the mix of service, product and domain employers hiring network support engineers in Coimbatore.
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01
After adding a new VLAN, users on one access switch cannot use it but others can. Why?
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.
02
Users behind a router can reach local servers but not the internet after a firewall change. NAT is configured. What do you check?
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.
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.
04
Tell me about a time you took initiative beyond your assigned work.
Situation: our team got many Wi-Fi complaints but had no data. Task: nobody had asked, but I wanted to find the cause. Action: I did a walk-through survey with a free tool, mapped channels and signal, and found three APs on the same 2.4 GHz channel and one dead AP. I shared a short report with fixes. Result: after the changes, Wi-Fi tickets dropped by about 60 percent in a month.
VLAN Trunking Protocol shares VLAN definitions from a server switch to clients in the same VTP domain. Modes are server, client, transparent and off. The risk is that a switch with a higher configuration revision number can overwrite and wipe VLANs across the domain. Many networks use transparent mode or VTP version 3 with a primary server to avoid this.
Put members in a channel group with mode active, then configure the port-channel.
interface range GigabitEthernet1/0/47 - 48
channel-group 1 mode active
interface Port-channel1
switchport mode trunk
switchport trunk allowed vlan 10,20,99
port-channel load-balance src-dst-ip
show etherchannel summary
07
What are the data plane, control plane and management plane?
The data plane forwards packets, using tables such as the FIB and MAC table, ideally in hardware. The control plane builds those tables using protocols like OSPF, STP and ARP. The management plane is how admins and tools interact with the device, through SSH, SNMP, syslog and APIs. Separating them helps understanding of SDN, where the control plane can be centralised.
08
How do you verify VLANs, trunks and MAC learning on a switch?
These show commands cover most VLAN troubleshooting.
show vlan brief
show interfaces trunk
show interfaces Gi1/0/5 switchport
show mac address-table vlan 20
show mac address-table address 0050.56ab.cdef
show interfaces status
They show VLAN membership, allowed and active VLANs on trunks, native VLAN and where each MAC was learned.
09
How do you do the basic initial configuration of a new switch?
Set the hostname, secure access and save the config.
enable
configure terminal
hostname SW1
enable secret Str0ngPass
service password-encryption
banner motd #Authorized access only#
line console 0
password ConPass
login
end
copy running-config startup-config
10
Describe a time you made a configuration mistake. How did you handle it?
Situation: I applied a /25 mask instead of /24 on a core VLAN interface during a change window. Task: fix it fast and own the error. Action: monitoring alerted on half the users, I checked my change, corrected the mask within ten minutes and informed my lead immediately. Result: impact was short, and I added a peer-review step and a pre-written rollback to every change plan afterwards.
11
Compare Ansible, Puppet and Chef for network automation.
Ansible is agentless, uses SSH or APIs, writes playbooks in YAML and uses a push model, so it is the most popular for network devices. Puppet uses an agent, a declarative manifest language and a pull model. Chef uses Ruby-based recipes with an agent and pull model. Puppet and Chef are more common for servers. All support idempotent configuration management.
12
Users suddenly receive IP addresses from a wrong subnet. What do you suspect and how do you fix it?
A rogue DHCP server, often a home router plugged into a wall port, is answering requests. I find it by checking the DHCP server IP on an affected client with ipconfig /all, then tracing its MAC with show mac address-table. I shut that port, and prevent it permanently by enabling DHCP snooping on user VLANs with only uplinks trusted.
13
A PC in VLAN 20 cannot reach a PC in VLAN 30. What do you check?
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.
14
What are the STP port states and timers in classic 802.1D?
States are blocking, listening, learning, forwarding and disabled. Timers are hello 2 seconds, forward delay 15 seconds and max age 20 seconds. A port moves from blocking through listening and learning, each 15 seconds, so convergence can take 30 to 50 seconds. That delay is why Rapid STP and PortFast are used in modern networks.
15
How do you configure NTP, syslog and SNMPv3 on a device?
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.
17
How do you configure IPv4 and IPv6 on a router interface?
Enable IPv6 routing globally, then add both addresses to the interface.
ipv6 unicast-routing
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ipv6 address 2001:db8:1:1::1/64
ipv6 address fe80::1 link-local
no shutdown
Verify with show ip interface brief and show ipv6 interface brief.
18
What is the difference between an access port and a trunk port?
An access port belongs to one VLAN and carries untagged frames, typically to PCs, printers or servers. A trunk port carries traffic for many VLANs between switches, routers or hypervisors, adding an 802.1Q tag to identify each frame's VLAN, except the native VLAN which is sent untagged. Access ports can also carry a separate voice VLAN for IP phones.
19
A host shows IP 169.254.12.5. What does this mean and what will you check?
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.
20
How do you prioritise when several tickets arrive at the same time?
Situation: on a night shift I got a core link down alert, two user tickets and a printer issue at once. Task: handle everything with minimum impact. Action: I prioritised by business impact, confirmed redundancy had taken over for the core link, raised a priority ticket with the carrier, then fixed the user tickets and logged the printer for morning. Result: no SLA was breached and the handover was clear.
Variable Length Subnet Masking means using different prefix lengths inside one address block, so each subnet is sized to its need. You allocate the largest subnets first, then smaller ones, to avoid overlaps. For example, from 10.1.1.0/24 you could give a 100-user LAN a /25, a 50-user LAN a /26, and point-to-point WAN links /30 or /31. It saves address space compared with fixed-length subnetting.
22
Your company is running out of IP addresses on a /24 user subnet. What options do you have?
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.
23
Voice calls are choppy during office hours when the WAN link is busy. How do you fix it?
Choppy voice under load means congestion on the WAN. I make sure phones mark RTP as EF and the access switches trust phone markings, then on the WAN router create a policy with a low latency priority queue for EF limited to the needed bandwidth, CBWFQ for other classes, and shaping to the real carrier rate so queuing happens on my router, not the provider's.
24
Guest Wi-Fi users must reach only the internet, not internal networks. How do you enforce it?
Put guests in their own VLAN and subnet, ideally terminating on a firewall or a separate VRF. Apply an inbound extended ACL on the guest SVI that permits DHCP and DNS to the allowed servers, denies all RFC 1918 destinations, and then permits any to the internet. Enable client isolation on the wireless side and rate limit the guest SSID so it cannot consume the WAN.
25
Traffic is not load balancing across two equal links even though both are in OSPF. What do you check?
Both paths must have equal total cost to be installed as ECMP. I check show ip route for two next hops. If only one shows, I compare interface costs, which differ if bandwidth or the reference bandwidth differs. I also check maximum-paths. Even with ECMP, load sharing is per flow using CEF, so a single large flow uses one link only.
DHCP Discover is a broadcast, and routers do not forward broadcasts, so a central DHCP server cannot hear clients on other subnets. A relay agent, configured with ip helper-address on the gateway interface, converts the broadcast into a unicast to the server and adds the gateway IP so the server picks the right scope. This lets one server serve many VLANs.
TCP is connection-oriented: it uses a three-way handshake, sequence numbers, acknowledgements, retransmission, windowing and flow control, so delivery is reliable and ordered. UDP is connectionless with an 8-byte header and no retransmission, so it is faster and lighter. HTTPS, SSH and SMTP use TCP; DNS queries, DHCP, SNMP, TFTP and voice or video RTP streams use UDP.
WPA2 uses AES-CCMP; WPA2-Personal uses a pre-shared key that is vulnerable to offline dictionary attacks, and WPA2-Enterprise uses 802.1X with RADIUS. WPA3-Personal replaces PSK with SAE, which resists offline guessing and gives forward secrecy. WPA3-Enterprise offers a 192-bit mode. WPA3 requires protected management frames. Open networks can use OWE for encryption without passwords.
Cost equals reference bandwidth divided by interface bandwidth. The default reference is 100 Mbps, so FastEthernet, Gigabit and 10 Gigabit all get cost 1, which hides the faster links. Change it with auto-cost reference-bandwidth 100000 on every router so 1G becomes 100 and 10G becomes 10. You can also set ip ospf cost directly on an interface. Path cost is the sum of outgoing interface costs.
30
What is a wildcard mask and how is it used in ACLs?
A wildcard mask tells the router which bits must match: 0 means must match and 1 means ignore. It is often the inverse of the subnet mask, so 192.168.1.0 0.0.0.255 matches the whole /24. host 10.1.1.1 equals 0.0.0.0 and any equals 255.255.255.255. Wildcards are also used in OSPF network statements. Calculate it by subtracting the mask from 255.255.255.255.
31
Explain the NAT terms inside local, inside global, outside local and outside global.
Inside local is the private address of an inside host, for example 192.168.1.10. Inside global is the public address that represents it outside, for example 203.0.113.5. Outside global is the real address of the remote host. Outside local is how the remote host appears to inside users, usually the same as outside global unless destination NAT is used. show ip nat translations displays these columns.
32
How do you write a simple Python script to fetch interface data from a device?
Netmiko handles SSH sessions; keep credentials in a file or vault, not the script.
import yaml
from netmiko import ConnectHandler
# r1.yml holds device_type, host, username, password
with open('r1.yml') as f:
device = yaml.safe_load(f)
with ConnectHandler(**device) as conn:
output = conn.send_command('show ip interface brief')
print(output)
33
How many usable hosts are in a /26 subnet and what is the block size?
A /26 leaves 6 host bits, so 2 to the power 6 is 64 addresses and 62 usable hosts after removing network and broadcast. The mask is 255.255.255.192 and the block size is 256 minus 192, which is 64. So subnets of 192.168.1.0/26 start at .0, .64, .128 and .192. For 192.168.1.70/26 the network is .64 and broadcast .127.
These commands cover neighbours, interfaces, routes and the database.
show ip ospf neighbor
show ip ospf interface brief
show ip ospf interface Gi0/0
show ip route ospf
show ip ospf database
show ip protocols
show ip protocols shows router ID, networks, passive interfaces and the reference bandwidth.
802.11n (Wi-Fi 4) works on 2.4 and 5 GHz with MIMO. 802.11ac (Wi-Fi 5) is 5 GHz only with wider channels and MU-MIMO downlink. 802.11ax (Wi-Fi 6 and 6E) adds OFDMA, BSS colouring and target wake time, and 6E adds the 6 GHz band. 802.11be (Wi-Fi 7) adds 320 MHz channels and multi-link operation. India opened part of the 6 GHz band for indoor use.
36
Users on a new floor report no network connectivity at all and the switch port LEDs are off. What is your approach?
No link light means a Layer 1 problem. I verify the switch has power and the ports are not administratively shut down with show ip interface brief. I test the cable with a tester, check the patch panel mapping and confirm the NIC is enabled. If the switch uses PoE for phones or access points, I also check the power budget with show power inline.
Few big employers listed in Coimbatore?
Many Coimbatore candidates also apply to teams in Chennai and to remote or hybrid roles. Practise the Chennai set as well.
Which companies hire CCNA professionals in Coimbatore?
Companies with large offices in Coimbatore include many IT services and product firms. Use their company pages below to practise employer-specific sets.
Are CCNA interviews in Coimbatore different from other cities?
The questions depend more on the company than the city. Coimbatore's mix of employers decides the style: Many roles are with delivery centres of bigger IT firms
How do I find CCNA jobs in Coimbatore?
Shortlist companies with Coimbatore offices, keep your CV focused on CCNA projects, apply on company career pages and job portals with the Coimbatore filter, and practise the questions on this page before each interview.