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Cognizant · Computer Networks
Practice Computer Networks questions specifically asked in Cognizant interviews – ideal for online test preparation, technical rounds and final HR discussions.
Questions
28
Tagged for this company + subject
Company
Cognizant
View company-wise questions
Subject
Computer Networks
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Go through each question and its explanation. Use this page for targeted revision just before your Cognizant Computer Networks round.
Bandwidth is the difference between the highest and lowest frequencies a channel can transmit. It represents the data-carrying capacity of a communication medium. A higher bandwidth allows more data to be sent per second, resulting in faster transmission speeds.
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Common noise types include thermal, impulse, cross-talk, and intermodulation noise. ‘Frame noise’ isn’t a recognized category. Understanding noise helps in applying filters, error correction, and improving reliability. It’s a classic physical layer interview topic.
In a star topology, all devices connect to a central hub or switch. This design makes troubleshooting easier since a failure in one cable affects only one device. However, if the central hub fails, the whole network can go down.
A WAN connects multiple local area networks over a wide geographic area using leased lines or satellites. The Internet itself is the largest WAN. Interviews often test your ability to distinguish LAN, MAN, and WAN by scale and technology.
CIDR replaced classful addressing by allowing variable-length subnet masks. This provides flexibility in allocating IP ranges and aggregates multiple routes into one, significantly reducing routing table sizes and conserving address space.
ARP translates IP addresses into MAC addresses so that data can be sent within a local area network. It enables communication between the Network Layer (IP) and Data Link Layer (MAC). Without ARP, IP packets could not reach their physical destination.
TCP establishes a connection before data transfer and ensures ordered, reliable delivery. UDP, by contrast, sends datagrams without connection setup, offering lower latency but no guarantee of delivery. Choosing between them depends on the application’s needs.
An analog signal changes smoothly over time, representing data through variations in amplitude or frequency. Examples include voice and radio waves. In contrast, digital signals use discrete values (0s and 1s). Understanding signal behavior helps explain how data is transmitted physically.
A switch works at the Data Link layer (Layer 2). It uses MAC addresses to forward frames between devices on the same network. Routers operate at Layer 3, while repeaters operate at Layer 1. Knowing device-to-layer mapping is a common quick-fire interview question.
Simple Mail Transfer Protocol (SMTP) handles sending of emails from clients to mail servers and between servers. POP3 and IMAP are used for retrieving emails. Interviewers often test your ability to distinguish these roles.
The Data Link Layer ensures reliable transfer of frames between two nodes connected by a physical link. It groups bits into frames, adds headers and trailers, detects errors, and sometimes handles retransmission. This layer bridges the gap between the raw transmission of bits and structured network communication.
The Hypertext Transfer Protocol (HTTP) governs how web clients (browsers) and servers exchange data such as HTML documents, images, and scripts. HTTPS is its secure version using SSL/TLS encryption to protect communication.
In Go-Back-N, if a frame or acknowledgment is lost, the sender goes back and retransmits that frame and all subsequent ones. It’s simpler to implement but less efficient than Selective Repeat, which retransmits only the missing frames.
An IP address uniquely identifies a host and its network on the Internet or a local network. It enables routers to make forwarding decisions and deliver packets correctly. Think of it as the device’s 'postal address' for digital communication.
Routing is the process of selecting paths in a network along which data packets travel from a source to a destination. Routers use routing tables and algorithms to decide the optimal path based on metrics like distance, cost, or congestion.
A routing table lists destination IP networks, their next-hop addresses, and the cost or metric to reach them. Routers refer to these tables to forward packets efficiently toward their destination.
Administrative Distance (AD) defines the trustworthiness of a route learned from a particular protocol. Lower AD values indicate more preferred routes. For example, OSPF has AD 110 while RIP has AD 120, so routers prefer OSPF routes when both exist.
In TCP socket programming, a client initiates a connection using connect(), while the server waits for requests using accept(). Once connected, data transfer uses send() and recv(). Understanding this flow helps you answer coding-based interview questions.
Server: socket(), bind(), listen(), accept() Client: socket(), connect()
Simple Network Management Protocol (SNMP) enables administrators to monitor device status, performance, and configuration using management information bases (MIBs). It’s critical in enterprise network maintenance and troubleshooting.
A firewall monitors and controls incoming and outgoing network traffic using predefined security rules. It acts as a barrier between trusted and untrusted networks, protecting against unauthorized access and attacks. Firewalls can be hardware, software, or both.
IPSec secures IP communication by authenticating and encrypting each IP packet in a communication session. It operates at the network layer and supports VPNs, ensuring confidentiality, data integrity, and origin authentication.
IEEE 802.11 defines wireless LAN (Wi-Fi) standards. It specifies how devices communicate wirelessly using radio waves in the 2.4 GHz or 5 GHz bands. Variants like 802.11n, 802.11ac, and 802.11ax improve speed and range.
Bluetooth is based on the IEEE 802.15.1 standard. It supports short-range communication using low-power radio waves, typically for personal area networks connecting devices like phones, headsets, and keyboards.
Ping sends ICMP echo requests to check if a host is reachable and measures round-trip time. It’s one of the simplest yet most useful troubleshooting tools to verify basic connectivity.
ping google.com
SD-WAN uses software intelligence to dynamically route traffic over the best available path (MPLS, broadband, or LTE). It enhances performance, reduces cost, and simplifies network management across distributed sites.
Congestion control prevents excessive load on the network that leads to packet loss and reduced throughput. TCP uses algorithms such as slow-start, congestion avoidance, fast retransmit, and fast recovery to adjust the sending rate based on perceived congestion.
An IDS detects and alerts administrators about suspicious activities, while an IPS goes a step further by automatically taking action to block or prevent attacks. Both systems are essential for layered network defense.
Network virtualization abstracts physical networking resources into logical networks. This allows flexible creation of isolated environments for different tenants or applications without changing hardware, improving scalability and utilization.