36 practice questions with answers for CCNA interviews in Visakhapatnam.
CCNA jobs in Visakhapatnam
Visakhapatnam (Vizag) has a developing IT market with delivery centres, start-ups and IT parks around Rushikonda. Many local candidates also apply to Hyderabad and remote roles, so a mix of service and product styles is common.
Below are 36 questions that match the mix of service, product and domain employers hiring network support engineers in Visakhapatnam.
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01
An EtherChannel shows members in suspended state. What do you check?
Suspended (s) usually means a configuration mismatch between members or with the far end. I compare speed, duplex, trunk mode, native VLAN and allowed VLANs on each member and the port-channel with show run interface, check LACP modes on both sides, and look at logs. I fix the config on the port-channel, then shut and no shut members so they rejoin. show etherchannel summary should show P flags.
A client asks its configured resolver, for example for www.example.com. If it is not cached, the resolver queries a root server, which refers it to the .com TLD server, which refers it to the authoritative server for example.com, which returns the A or AAAA record. The answer is cached for its TTL. DNS uses UDP 53 for most queries and TCP 53 for zone transfers and large replies.
03
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.
04
How do you quickly calculate how many subnets and hosts a mask gives?
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.
Physical ports include service ports for out-of-band management, distribution system ports that connect to the switch as trunks, and redundancy ports for HA. Logical interfaces include the management interface used for CAPWAP and admin access, dynamic interfaces that map WLANs to VLANs, and a virtual interface used for web auth and DHCP relay. A LAG bundles distribution ports.
07
Tell me about a time you found a security issue and reported it.
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.
08
A broadcast storm brought the network down after someone connected a cable between two wall ports. How do you prevent this?
Two wall ports patched to the same switch formed a loop. To stop it now, I find the port with rising broadcast counters and shut it. To prevent repeats, enable PortFast with BPDU Guard on all access ports, keep Rapid PVST+ running everywhere, add storm-control broadcast thresholds on access ports and enable errdisable recovery with a sensible interval.
09
Describe a situation where you had to explain a technical issue to a non-technical manager.
Situation: a routing loop during a carrier change caused a two-hour outage and the operations head wanted an explanation. Task: explain cause and prevention simply. Action: I used a road map analogy, explained that two routers kept sending traffic to each other, showed the timeline and our fix, and listed three prevention steps with dates. Result: management approved a proper change review board, and trust in our team improved.
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.
11
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)
12
What is SLAAC and how is it different from DHCPv6?
With SLAAC a host learns the /64 prefix from a router advertisement and builds its own interface ID, without a server. Stateless DHCPv6 adds extra options such as DNS while the address still comes from SLAAC. Stateful DHCPv6 assigns the address itself and keeps bindings, similar to DHCPv4. RA flags M (managed) and O (other config) tell hosts which method to use.
13
What is the difference between a two-tier and a three-tier campus design?
A three-tier design has access, distribution and core layers: access connects users, distribution aggregates access switches and applies policy, and the core provides fast transport between distribution blocks. A two-tier or collapsed-core design merges core and distribution, which suits small and medium campuses with fewer buildings. Three-tier scales better when there are many distribution blocks.
14
Which commands would you use to test end-to-end reachability and find where packets stop?
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.
15
How do you handle a change that must be done during a night window?
Situation: we had to migrate 30 access ports to new VLANs overnight. Task: finish with zero business impact. Action: I prepared configs in advance, got peer review, scheduled a rollback, informed the helpdesk and tested each floor with a laptop after changes. Result: the migration finished an hour early, morning tickets were zero, and the plan became our template for later VLAN changes.
Set a router ID, enable OSPF on interfaces and make user ports passive.
router ospf 1
router-id 1.1.1.1
auto-cost reference-bandwidth 100000
passive-interface GigabitEthernet0/1
network 10.0.12.0 0.0.0.3 area 0
network 192.168.1.0 0.0.0.255 area 0
default-information originate
Or per interface: ip ospf 1 area 0
A Layer 3 switch forwards packets between VLANs in hardware using SVIs or routed ports, giving very high throughput with many Ethernet ports. A router usually has fewer ports but richer WAN features such as NAT, VPN, deep QoS, varied WAN interfaces and large routing tables. In campuses, Layer 3 switches handle inter-VLAN routing while routers or firewalls handle the edge.
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.
Rapid PVST+ runs 802.1w per VLAN. It uses a proposal and agreement handshake on point-to-point links so ports move to forwarding in under a second, instead of waiting on timers. It has port roles root, designated, alternate and backup, and states discarding, learning and forwarding. Alternate ports provide an instant backup root port. It is the default on most modern IOS switches.
21
How does controller-based networking differ from traditional networking?
Traditionally each device has its own control plane and is configured box by box. In controller-based or software-defined networking, a central controller holds the policy and pushes it to devices through southbound APIs such as NETCONF or OpenFlow, while applications talk to the controller through northbound REST APIs. This gives consistent configuration, automation and network-wide visibility.
22
What is the difference between standard and extended ACLs?
Standard ACLs (1 to 99 and 1300 to 1999) match only the source IP, so they should be placed close to the destination. Extended ACLs (100 to 199 and 2000 to 2699) match protocol, source, destination and ports, so they can be placed close to the source to drop unwanted traffic early. Named ACLs work for both and allow editing individual lines by sequence number.
23
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.
A voice VLAN lets an IP phone and a PC share one switch port while keeping their traffic separate. The port is an access port in the data VLAN, and the switch tells the phone through CDP or LLDP-MED to tag voice frames with the voice VLAN. This allows QoS priority for voice and separate addressing. Configure it with switchport voice vlan.
RFC 3021 allows /31 on point-to-point links because there is no need for network and broadcast addresses when only two devices exist. A /31 gives exactly two usable addresses, saving half the space of a /30. It is common on ISP and data center fabric links. Both ends must support it; on IOS you simply configure ip address 10.0.0.0 255.255.255.254.
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.
DHCP uses the DORA process: the client broadcasts Discover, the server answers with an Offer, the client broadcasts a Request for that offer, and the server confirms with an Acknowledgement. The lease includes IP, mask, gateway, DNS servers and lease time. Clients renew at 50 percent of the lease. DHCP uses UDP ports 67 for the server and 68 for the client.
28
How would you represent an interface configuration in JSON and YAML?
The same data in both formats.
JSON:
{
"interface": "GigabitEthernet0/1",
"enabled": true,
"ipv4": ["192.168.1.1/24"]
}
YAML:
interface: GigabitEthernet0/1
enabled: true
ipv4:
- 192.168.1.1/24
29
A newly configured router interface rejects the IP 192.168.5.64/26. Why?
With a /26 the block size is 64, so 192.168.5.64 is the network address of the subnet .64 to .127 and cannot be assigned to a host or interface. IOS reports a bad mask or overlap error. Use a usable address such as 192.168.5.65 instead. Similarly .127 would be the broadcast. Always calculate the subnet boundary before configuring addresses.
30
How do you check interface status and errors on an IOS device?
show ip interface brief gives status and IP of all interfaces, and show interfaces gives counters and duplex.
Router# show ip interface brief
Router# show interfaces GigabitEthernet0/1
Router# show interfaces status
Router# clear counters GigabitEthernet0/1
Status up/down means Layer 1 is up but Layer 2 keepalives fail; administratively down means the interface is shut.
NDP uses ICMPv6 messages. A host sends a Neighbor Solicitation to the target's solicited-node multicast address (ff02::1:ffXX:XXXX) and gets a Neighbor Advertisement with the MAC. Router Solicitation and Router Advertisement messages provide prefix and gateway. Duplicate Address Detection uses NS to check that an address is unique. Using multicast instead of broadcast reduces load on other hosts.
Allow web traffic from one subnet to a server and block the rest of that subnet.
ip access-list extended WEB-ONLY
10 permit tcp 192.168.10.0 0.0.0.255 host 10.0.0.80 eq 443
20 deny ip 192.168.10.0 0.0.0.255 10.0.0.0 0.0.0.255
30 permit ip any any
interface vlan 10
ip access-group WEB-ONLY in
show access-lists WEB-ONLY
33
What is port security and what are its violation modes?
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.
Exclude static addresses first, then define the pool.
ip dhcp excluded-address 192.168.10.1 192.168.10.20
ip dhcp pool VLAN10
network 192.168.10.0 255.255.255.0
default-router 192.168.10.1
dns-server 8.8.8.8 1.1.1.1
lease 7
show ip dhcp binding
show ip dhcp pool
35
How do you configure AAA with TACACS+ and a local fallback?
Define the server, then method lists with local as backup.
aaa new-model
tacacs server ISE1
address ipv4 10.0.0.60
key Tac@csKey1
aaa authentication login default group tacacs+ local
aaa authorization exec default group tacacs+ local
aaa accounting commands 15 default start-stop group tacacs+
username breakglass privilege 15 secret L0calOnly!
36
What are the first hop redundancy protocols and how does HSRP work?
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.
Few big employers listed in Visakhapatnam?
Many Visakhapatnam candidates also apply to teams in Hyderabad and to remote or hybrid roles. Practise the Hyderabad set as well.
Which companies hire CCNA professionals in Visakhapatnam?
Companies with large offices in Visakhapatnam include many IT services and product firms. Use their company pages below to practise employer-specific sets.
Are CCNA interviews in Visakhapatnam different from other cities?
The questions depend more on the company than the city. Visakhapatnam's mix of employers decides the style: Many local candidates also apply to Hyderabad and remote roles, so a mix of service and product styles is common
How do I find CCNA jobs in Visakhapatnam?
Shortlist companies with Visakhapatnam offices, keep your CV focused on CCNA projects, apply on company career pages and job portals with the Visakhapatnam filter, and practise the questions on this page before each interview.