38 Networking interview questions with answers (2026)

All Networking interview questions

What is the OSI 7-layer model? What is the function of each layer?

How does the TCP/IP model differ from the OSI model?

How does the TCP 3-way handshake work? Why are 3 steps necessary?

How does DNS work? Explain the process of resolving a domain name.

How does WebSocket differ from regular HTTP? When should you use WebSocket?

How do REST, GraphQL, and gRPC differ? When should you use each?

What are the common load balancing algorithms? What are the pros and cons of each?

How do reverse proxy and forward proxy differ? Why is reverse proxy important in production?

How does a CDN work? When should and should not you use a CDN?

What is CORS? Explain the preflight request mechanism and how to configure it correctly.

What is rate limiting? What are common rate limiting strategies and how do you implement them?

Compare API authentication methods: OAuth2, JWT, and API Key. When should you use each?

What challenges does WebSocket scaling present? How do you solve them in a multi-server system?

Server-Sent Events (SSE) vs WebSocket vs Long Polling: comparison and when to use each?

How does TCP 4-way handshake (connection teardown) work? What is the TIME_WAIT state?

IPv4 vs IPv6: key differences and why has the transition been slow?

How does TLS 1.3 differ from TLS 1.2? Why is TLS 1.3 recommended?

What is Mutual TLS (mTLS)? When is it needed in microservices?

Important HTTP status codes: distinguish 401 vs 403, 502 vs 504, and 3xx redirects?

What are subnetting and CIDR notation? How do you calculate subnets in practice?

L4 vs L7 load balancers: how do they differ and when should you use each?

Latency vs Bandwidth vs Throughput: how do they differ and how do you optimize each?

HTTP Keep-Alive and Connection Pooling: the mechanism and performance impact?

Cache-Control headers: no-cache vs no-store vs max-age, how do ETag and Last-Modified work?

Connection timeout vs Read timeout vs Write timeout: differences and correct configuration?

How does ARP work? When does a host need to send an ARP request?

How does DHCP assign IP addresses dynamically? Explain the four DORA steps.

What is NAT? What problem does it solve?

How do private and public IP addresses differ? What are the private ranges?

How do MAC and IP addresses differ? Why are both needed?

How do a hub, a switch, and a router differ? At which layer does each operate?

How do TCP flow control and congestion control differ? How does the sliding window work?

What is ICMP? How do ping and traceroute work?

How do encapsulation and decapsulation happen as a packet travels through the network stack (TCP/IP model)?

How do symmetric and asymmetric encryption differ? Why does TLS use both?

How do VPNs and tunneling work?

How do static and dynamic routing differ? Compare OSPF with RIP; what is a default gateway?

What are well-known ports? Name a few common ones.

All Networking interview questions

What is the OSI 7-layer model? What is the function of each layer?
How does the TCP/IP model differ from the OSI model?
How does the TCP 3-way handshake work? Why are 3 steps necessary?
How does DNS work? Explain the process of resolving a domain name.
How does WebSocket differ from regular HTTP? When should you use WebSocket?
How do REST, GraphQL, and gRPC differ? When should you use each?
What are the common load balancing algorithms? What are the pros and cons of each?
How do reverse proxy and forward proxy differ? Why is reverse proxy important in production?
How does a CDN work? When should and should not you use a CDN?
What is CORS? Explain the preflight request mechanism and how to configure it correctly.
What is rate limiting? What are common rate limiting strategies and how do you implement them?
Compare API authentication methods: OAuth2, JWT, and API Key. When should you use each?
What challenges does WebSocket scaling present? How do you solve them in a multi-server system?
Server-Sent Events (SSE) vs WebSocket vs Long Polling: comparison and when to use each?
How does TCP 4-way handshake (connection teardown) work? What is the TIME_WAIT state?
IPv4 vs IPv6: key differences and why has the transition been slow?
How does TLS 1.3 differ from TLS 1.2? Why is TLS 1.3 recommended?
What is Mutual TLS (mTLS)? When is it needed in microservices?
Important HTTP status codes: distinguish 401 vs 403, 502 vs 504, and 3xx redirects?
What are subnetting and CIDR notation? How do you calculate subnets in practice?
L4 vs L7 load balancers: how do they differ and when should you use each?
Latency vs Bandwidth vs Throughput: how do they differ and how do you optimize each?
HTTP Keep-Alive and Connection Pooling: the mechanism and performance impact?
Cache-Control headers: no-cache vs no-store vs max-age, how do ETag and Last-Modified work?
Connection timeout vs Read timeout vs Write timeout: differences and correct configuration?
How does ARP work? When does a host need to send an ARP request?
How does DHCP assign IP addresses dynamically? Explain the four DORA steps.
What is NAT? What problem does it solve?
How do private and public IP addresses differ? What are the private ranges?
How do MAC and IP addresses differ? Why are both needed?
How do a hub, a switch, and a router differ? At which layer does each operate?
How do TCP flow control and congestion control differ? How does the sliding window work?
What is ICMP? How do ping and traceroute work?
How do encapsulation and decapsulation happen as a packet travels through the network stack (TCP/IP model)?
How do symmetric and asymmetric encryption differ? Why does TLS use both?
How do VPNs and tunneling work?
How do static and dynamic routing differ? Compare OSPF with RIP; what is a default gateway?
What are well-known ports? Name a few common ones.