What should you focus on for a computer networks interview?
Which topics came up most in these interviews?
Troubleshooting, design, and operations appeared in 115 of 337 interviews. HTTP, APIs, and WebSocket appeared in 104 of 337 interviews. Start with practical network problems and web requests, rather than only protocol definitions.
- Can you explain which diagnostic tools you would use for an outage?
- Can you describe how you would plan network capacity, upgrades, and change control?
- Can you trace a web request and explain HTTP methods and status codes?
Also check security and addressing: can you explain firewall rules, VPN tunnels, subnets, gateways, and DNS?
Which basic questions should you be able to answer?
The questions about switches, routers, and firewalls and about the OSI model were the most asked individual questions in these interviews. Use the checks below to test both your definitions and your choices.
- Can you explain how a switch, router, and firewall differ?
- Can you name the OSI layers and explain the TCP/IP model?
- Can you choose TCP or UDP for an application and explain your choice?
- Can you explain why you would separate groups of devices with VLANs?
- Can you describe DHCP and walk through the TCP handshake?
What should you check in your web networking answers?
Check the full request flow as well as individual terms:
- Can you describe what happens from entering a URL to receiving and rendering the page?
- Can you explain how HTTP and HTTPS differ on the wire?
- Can you explain what common HTTP status codes mean?
Make the PUT and PATCH difference clear. In reviews of real answers, 3 of 8 answers missed this distinction: PUT replaces the full resource at a known URL, while PATCH makes a partial update. Can you explain which method you would use for each kind of update?
Which coding tasks are worth checking?
Coding tasks appeared in 3 of 337 interviews. Use the tasks from these interviews as concrete checks:
- Can you pass parameters in a Python HTTP request and retrieve the response?
- Can you fetch data from a public API and show it in a list?
- Can you make a message entered in one browser appear in another browser?
Who gets asked Computer Networks
The 20 most asked Computer Networks questions
Counted by interview, not by mention: a question asked twice in one conversation counts once.
How do switches, routers, and firewalls differ?
Asked in 9 of 337 interviews · last asked Oct 13 · Concept · Junior
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A switch connects devices within a local network and forwards frames using MAC addresses. A router connects different networks and forwards packets using IP addresses. A firewall allows or blocks traffic based on security rules. One device can perform more than one of these roles.
- Switches usually work at Layer 2; Layer 3 switches can also route traffic.
- Routers choose paths between IP networks using routing tables.
- Firewalls can filter by addresses, ports, connection state, or application data.
What the interviewer checks: The interviewer is checking whether you can separate local forwarding, routing between networks, and security filtering.
Other ways it was asked
- “What distinguishes a switch from a router?”
- “How would you explain the difference between a switch, a router, and a firewall?”
- “Can you tell me the difference between a switch and a router?”
What is the OSI model, and what are its layers?
Asked in 9 of 337 interviews · last asked Sep 29 · Concept · Junior
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The OSI (Open Systems Interconnection) model is a reference model that divides network communication into seven layers. From bottom to top, they are Physical, Data Link, Network, Transport, Session, Presentation, and Application. It helps explain network functions and troubleshoot problems.
- Physical sends raw bits; Data Link handles frames and delivery over a local link.
- Network handles logical addressing and routing; Transport handles end-to-end data delivery between applications.
- Session manages communication sessions; Presentation handles data formats, encryption, and compression.
- Application provides network services to software. Real protocols do not always fit neatly into OSI layers.
What the interviewer checks: The interviewer checks whether you know the layer order, each layer’s role, and the model’s purpose.
Other ways it was asked
- “What is the OSI model?”
- “Can you explain the OSI reference model?”
- “Tell me about the OSI model.”
How do TCP and UDP differ, and when would you choose each for an application?
Asked in 8 of 337 interviews · last asked Oct 12 · Concept · Junior
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TCP is connection-oriented and provides reliable, ordered delivery of bytes. UDP sends separate packets without guaranteeing delivery or order. Choose TCP when complete, ordered data matters, such as file transfers. Choose UDP when late data is less useful than missing data, such as live calls, or when the application handles reliability itself.
- TCP retransmits lost data and includes flow control and congestion control.
- TCP is a byte stream; UDP preserves message boundaries.
- UDP has less protocol overhead, but it is not always faster.
- UDP applications must handle loss and reordering if these matter.
What the interviewer checks: The interviewer checks whether you can match delivery guarantees and delay needs to an application's requirements.
Other ways it was asked
- “What is the difference between TCP and UDP?”
- “Can you tell me the difference between TCP and UDP?”
- “What is the difference between UDP and TCP?”
What is HTTPS, and how does it differ from HTTP on the wire?
Asked in 8 of 337 interviews · last asked Sep 21 · Concept · Junior
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HTTPS is HTTP protected by TLS. Unlike plain HTTP, it sends HTTP headers and bodies as encrypted data. A TLS handshake sets up encryption and normally checks the server's certificate. This protects against reading or changing traffic in transit.
- HTTP uses port 80 by default; HTTPS uses port 443.
- The client checks that the server certificate is trusted and matches the requested hostname.
- IP addresses remain visible, and the hostname may still be exposed.
- HTTP/1.1 and HTTP/2 use TLS over TCP for HTTPS; HTTP/3 uses QUIC with integrated TLS over UDP.
What the interviewer checks: The interviewer checks whether you understand encryption, server identity checks, and what changes on the wire.
Other ways it was asked
- “What is the difference between HTTP and HTTPS?”
- “What is HTTPS?”
- “What's the difference between HTTP and HTTPS, and what actually happens differently on the wire?”
What is a VLAN, and why would you use VLANs to separate groups of devices?
Asked in 6 of 337 interviews · last asked Oct 21 · Concept · Junior
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A VLAN, or Virtual Local Area Network, splits a physical network into separate logical networks. Each VLAN has its own broadcast domain, so broadcasts stay within that VLAN. VLANs separate groups such as staff, guests, and servers, reduce broadcast traffic, and allow access rules between groups.
- Devices can share physical switches while belonging to different VLANs.
- Traffic between VLANs needs routing, with firewall rules or access lists to control access.
- Trunk links usually use IEEE 802.1Q tags to carry traffic for multiple VLANs.
- VLANs provide separation, not encryption.
What the interviewer checks: The interviewer checks whether you understand logical separation, broadcast boundaries, and how traffic moves between VLANs.
Other ways it was asked
- “What is a VLAN?”
- “What is a VLAN, in your own words?”
- “What are VLANs, and how do they work?”
What is DHCP?
Asked in 6 of 337 interviews · last asked Oct 21 · Concept · Junior
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DHCP stands for Dynamic Host Configuration Protocol. It automatically gives devices an IP address and other network settings, such as a subnet mask, default gateway, and DNS servers. IP addresses are usually leased for a limited time and can be renewed.
- DHCP reduces manual setup and mistakes in network settings.
- DHCPv4 typically uses four steps: Discover, Offer, Request, and Acknowledge.
- DHCPv4 uses UDP port 67 on the server and port 68 on the client.
What the interviewer checks: The interviewer is checking whether you understand how devices automatically receive their network settings.
Other ways it was asked
- “Could you explain DHCP?”
- “What can you tell me about DHCP?”
- “What is the meaning of DHCP?”
How does the TCP three-way handshake work, including for HTTP/1 and HTTP/2 connections?
Asked in 6 of 337 interviews · last asked Oct 16 · Concept · Junior
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The client sends SYN, the server replies with SYN-ACK, and the client sends ACK. This establishes a TCP connection and exchanges starting sequence numbers for both directions. HTTP/1 and HTTP/2 use this handshake when opening a new TCP connection. They can reuse that connection for multiple requests.
- SYN-ACK acknowledges the client's SYN; the final ACK acknowledges the server's SYN.
- For HTTPS, TLS setup follows TCP setup, before normal HTTP traffic.
- HTTP/2 can carry multiple active request streams over one TCP connection.
- Repeated SYN packets without SYN-ACK suggest packet loss, filtering, or an unreachable server; RST can indicate connection refusal.
What the interviewer checks: The interviewer checks whether you understand TCP setup, packet traces, and how HTTP and TLS use TCP.
Other ways it was asked
- “What is the TCP three-way handshake?”
- “Can you explain the TCP three-way handshake?”
- “What happens during the TCP three-way handshake?”
What happens from entering a URL in a browser to receiving and rendering the page?
Asked in 6 of 337 interviews · last asked Aug 25 · Concept · Mid-level
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The browser checks caches and uses DNS if it needs the server's IP address. It reuses or opens a connection: usually TCP, with TLS for HTTPS; HTTP/3 uses QUIC. It sends an HTTP request and receives a response. For HTML, it parses the document, fetches resources, runs scripts, and calculates and draws the page layout.
- Cached content, cached DNS results, and existing connections can skip some network steps.
- HTTPS encrypts traffic and verifies the server's certificate; HTTP/3 uses QUIC over UDP with TLS.
- The server processes the request and returns a status, headers, and usually a body; redirects require another request.
- HTML builds the DOM; CSS determines styles. Layout calculates positions, and painting draws content.
What the interviewer checks: The interviewer checks whether you can connect DNS, transport security, HTTP, and browser rendering in the right order.
Other ways it was asked
- “What happens on the networking side when you type a URL into a browser?”
- “What happens behind the scenes from a networking and web browsing perspective when you type a URL into a browser?”
- “What happens after you enter google.com in a browser and submit the request? Which services are involved, and where does the information go?”
What is TCP?
Asked in 5 of 337 interviews · last asked Sep 9 · Concept · Junior
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TCP stands for Transmission Control Protocol. It is a connection-oriented transport-layer protocol that provides reliable, ordered delivery of a byte stream between applications. It detects lost data and retransmits it, while using flow control and congestion control to manage transmission.
- TCP establishes a connection, usually with a three-way handshake.
- Sequence numbers and acknowledgments support ordered delivery and retransmission.
- Flow control protects the receiver; congestion control limits pressure on the network.
- TCP carries a byte stream, so it does not preserve message boundaries.
What the interviewer checks: The interviewer is checking whether you understand TCP’s role, reliability, connection setup, and basic traffic controls.
Other ways it was asked
- “What does TCP mean?”
- “What is the TCP protocol?”
- “What does TCP stand for, and what is it?”
What do common HTTP status codes mean?
Asked in 5 of 337 interviews · last asked Oct 5 · Concept · Junior
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HTTP status codes are three-digit numbers that describe an HTTP response. The groups are 1xx for information, 2xx for success, 3xx for redirection, 4xx for client errors, and 5xx for server errors.
- 200: OK; 201: resource created; 204: success with no response body.
- 301: permanent redirect; 302: temporary redirect; 304: not modified, so reuse the cached response.
- 400: bad request; 401: missing or invalid credentials; 403: forbidden; 404: not found; 429: too many requests.
- 500: internal server error; 502: gateway received an invalid upstream response; 503: service temporarily unavailable.
What the interviewer checks: The interviewer checks whether you understand response outcomes and can distinguish authentication, permission, client, and server problems.
Other ways it was asked
- “What are HTTP status codes?”
- “What are the different HTTP response status codes?”
- “What are the common HTTP status codes?”
What is a VPN, and what is it used for?
Asked in 5 of 337 interviews · last asked Sep 2 · Concept · Junior
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A VPN (Virtual Private Network) creates a private connection over a shared network, usually through an encrypted tunnel. It is used to access company resources remotely, connect office networks, and protect traffic on public Wi-Fi. Depending on its settings, it carries all traffic or only selected traffic.
- Remote-access VPNs connect users to a network; site-to-site VPNs connect networks.
- VPN encryption protects traffic between the device or network and the VPN gateway.
- A VPN can hide your public IP address from websites, but it does not guarantee anonymity.
What the interviewer checks: The interviewer checks whether you understand VPN tunnels, their main uses, and their privacy limits.
Other ways it was asked
- “What are VPNs, and what are they used for?”
- “What is a VPN, and how does it work?”
- “What is a VPN?”
What is the difference between a dynamic IP address and a static IP address?
Asked in 4 of 337 interviews · last asked Sep 24 · Concept · Junior
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A static IP address stays fixed until someone changes its configuration. A dynamic IP address is assigned automatically, usually by DHCP, and may change over time. Static addresses help devices stay reachable at a known address, while dynamic addresses reduce manual setup.
- DHCP-assigned addresses use leases; renewing a lease does not always change the address.
- Static addresses are useful for servers and other devices that need predictable addresses.
- A DHCP reservation can give a device the same address automatically.
What the interviewer checks: The interviewer is checking whether you understand address stability, DHCP assignment, and when each type is useful.
Other ways it was asked
- “What is the difference between a static and a dynamic IP address?”
- “What is the difference between a static and dynamic IP address?”
Can you describe DNS?
Asked in 4 of 337 interviews · last asked Oct 21 · Concept · Junior
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DNS stands for Domain Name System. It translates domain names, such as example.com, into IP addresses that computers use to connect. It is a distributed, hierarchical system that also stores records for services such as email. DNS resolvers look up records and cache them to speed up later requests.
- DNS uses a hierarchy of root servers, top-level domain servers, and authoritative servers.
- A records hold IPv4 addresses; AAAA records hold IPv6 addresses; MX records identify mail servers.
- Cached records have a time to live, or TTL, which limits how long they remain valid.
- DNS commonly uses UDP port 53, but also uses TCP port 53.
What the interviewer checks: The interviewer is checking whether you understand name resolution, the DNS hierarchy, and caching.
Other ways it was asked
- “What is DNS?”
- “What can you tell me about DNS?”
What is UDP?
Asked in 4 of 337 interviews · last asked Jul 29 · Concept · Junior
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UDP (User Datagram Protocol) is a connectionless transport-layer protocol that sends data as separate packets called datagrams. It does not guarantee delivery, order, or protection against duplicates. Its low overhead suits uses such as DNS queries, live audio and video, and online games.
- No connection setup is required before sending data.
- UDP preserves message boundaries but does not retransmit lost packets.
- Applications must handle missing or out-of-order data if needed.
- DNS commonly uses UDP, but it also uses TCP.
What the interviewer checks: The interviewer is checking whether you understand UDP’s delivery limits and why applications choose it over TCP.
Other ways it was asked
- “What can you tell me about UDP?”
- “What is UDP, and what type of protocol is it?”
- “What are some applications that use UDP?”
How does BGP prevent routing loops?
Asked in 4 of 337 interviews · last asked Sep 29 · Concept · Mid-level
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BGP normally rejects a route if its AS_PATH contains the local AS number. Within an AS, iBGP does not advertise routes learned from one iBGP peer to another by default. Route reflectors relax this rule and use ORIGINATOR_ID and CLUSTER_LIST to prevent loops.
- eBGP normally adds the local AS number to AS_PATH when advertising a route; iBGP does not.
- Without route reflectors or confederations, iBGP needs a full mesh of peer connections.
- Route reflectors reject routes with their own router ID as ORIGINATOR_ID or their cluster ID in CLUSTER_LIST.
- When redistributing between OSPF and BGP, use route tags and filters to prevent routes feeding back.
What the interviewer checks: The interviewer checks whether you understand both AS-level loop detection and loop prevention within iBGP.
Other ways it was asked
- “How does iBGP prevent routing loops, apart from checking the AS path?”
- “What mechanism does BGP use to prevent routing loops?”
- “How would you prevent routing loops in a network running OSPF and BGP?”
Which BGP attributes can you use to influence outbound traffic routing?
Asked in 4 of 337 interviews · last asked Jul 31 · Concept · Mid-level
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Use LOCAL_PREF to choose the preferred outbound link across your AS. On Cisco routers, weight can override that choice on one router only. For inbound traffic, use AS_PATH prepending, MED, or provider-supported BGP communities. These influence how other networks reach you, but their routing policies can override your preferences.
- Higher LOCAL_PREF wins and applies across your AS.
- Higher Cisco weight wins before LOCAL_PREF, but affects only the local router.
- AS_PATH prepending makes an advertised path longer and usually less attractive.
- Lower MED is preferred, but it is normally compared only between routes from the same neighboring AS.
What the interviewer checks: The interviewer checks whether you distinguish outbound route control from inbound influence and understand each attribute’s scope.
Other ways it was asked
- “Which BGP attributes can you use to influence inbound traffic routing?”
- “Which BGP attributes can you use to manipulate route selection?”
- “What BGP options can you use to influence route selection for inbound versus outbound traffic?”
Can you explain BGP?
Asked in 4 of 337 interviews · last asked Aug 19 · Concept · Junior
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BGP (Border Gateway Protocol) is a path-vector routing protocol that exchanges routes between autonomous systems, such as ISP networks. It advertises IP address ranges and selects routes using policies and path attributes, not just distance. It is used for Internet routing and connecting a network to multiple providers.
- An autonomous system is a network or group of networks under one routing administration.
- eBGP exchanges routes between autonomous systems; iBGP shares BGP routes within one autonomous system.
- BGP peers establish connections using TCP port 179.
- The AS_PATH attribute lists autonomous systems along a route and helps prevent routing loops.
What the interviewer checks: The interviewer checks whether you understand BGP’s role in Internet routing and its policy-based route selection.
Other ways it was asked
- “What is BGP, and when would you use it?”
- “How does BGP work?”
- “What is BGP?”
After a customer approves a vendor's firewall access, what should happen before the change, and how would you verify it afterward?
Asked in 4 of 337 interviews · last asked Oct 12 · Scenario · Mid-level
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Before changing the firewall, follow the change process: record approval, confirm the exact access needed, and agree on a change window. Back up the configuration and prepare a rollback plan. Afterward, test the vendor connection, check firewall logs, and confirm unauthorized access remains blocked. Get customer or vendor confirmation, document the results, and close the change ticket.
- Confirm source and destination addresses, ports, protocol, and direction; allow only the required access.
- Obtain any required internal change approval and notify affected teams before implementation.
- Test from the vendor’s actual connection and verify the intended application works.
- Record the final rules and test results; set an expiry if access is temporary.
What the interviewer checks: The interviewer is checking whether you follow change control, limit access, verify results, and document completion.
Other ways it was asked
- “After a customer approves a vendor connection to its environment, what must happen before changing the firewall?”
- “Once a firewall change for vendor access is authorized, how do you verify it worked and close out the change?”
- “After a customer approves a firewall port change for vendor access, what steps should happen before the change, and how would you verify and close it out?”
Can you explain the difference between single-mode and multimode fiber?
Asked in 3 of 337 interviews · last asked Apr 7 · Concept · Junior
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Single-mode fiber has a small core and carries one light mode, so it supports longer distances. Multimode fiber has a larger core and carries several light modes, which spread out and limit distance. Multimode is common for short links inside buildings, while single-mode is common for long-distance links.
- Single-mode cores are about 9 micrometers wide; multimode cores are usually 50 or 62.5 micrometers.
- Multimode has modal dispersion: different light paths cause pulses to spread out.
- Multimode transceivers are often cheaper, but total cost depends on speed and distance.
- Both support high speeds; maximum reach depends on the fiber type and transceivers.
What the interviewer checks: The interviewer checks whether you can connect core size and light modes to distance, speed, and cost.
Other ways it was asked
- “What are the differences between multimode and single-mode fiber?”
- “What is the difference between single-mode and multimode fiber?”
What are the IPv4 address classes?
Asked in 3 of 337 interviews · last asked Sep 24 · Concept · Junior
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IPv4 has five historical address classes, based on the first octet: A (0–127), B (128–191), C (192–223), D (224–239), and E (240–255). Classes A, B, and C were for unicast addressing; D is for multicast, and E is reserved. Modern networks use CIDR instead of classes.
- Default masks were A: 255.0.0.0 (/8), B: 255.255.0.0 (/16), and C: 255.255.255.0 (/24).
- Class A’s usual first-octet range is 1–126; 0 has special uses, and 127 is for loopback.
- 255.255.255.255 is the limited broadcast address, an exception within the Class E range.
- CIDR uses a prefix length to define the network boundary, rather than an address class.
What the interviewer checks: The interviewer checks whether you know the class ranges, their uses, and how CIDR replaced class-based addressing.
Other ways it was asked
- “What are the different IPv4 address classes, and what are their ranges?”
- “How many IPv4 address classes are there?”
- “Which IPv4 address classes are there?”
Computer networking basics interview questions
Questions cover network concepts, client-server communication, topologies, network devices, OSI layers, and the TCP/IP model. 56 questions.
What is the primary difference between Layer 2 and Layer 3?
Asked in 2 of 337 interviews · last asked Aug 4 · Concept · Junior
Other ways it was asked
- “What is the difference between a Layer 2 switch and a Layer 3 switch?”
What does LAN stand for, and how would you define a LAN?
Asked in 2 of 337 interviews · last asked Oct 21 · Concept · Junior
Other ways it was asked
- “What is a LAN, and what is a network?”
What is network topology, and what are its types?
Asked in 2 of 337 interviews · last asked Jul 26 · Concept · Junior
Other ways it was asked
- “What is network topology?”
What are the functions of the data link layer?
Asked in 2 of 337 interviews · last asked Mar 28 · Concept · Junior
How many layers are present in the TCP/IP model?
Asked in 2 of 337 interviews · last asked Jul 29 · Concept · Junior
Other ways it was asked
- “How many layers are there in the TCP/IP protocol suite?”
What is full-duplex communication?
Asked in 2 of 337 interviews · last asked Jul 16 · Concept · Junior
Other ways it was asked
- “What are half-duplex and full-duplex communication?”
Can you explain the concept of a network?
Asked in 2 of 337 interviews · last asked Aug 11 · Concept · Junior
Other ways it was asked
- “What is network?”
How would you define the difference between the data plane and the control plane?
Asked once · last asked Jul 16 · Concept · Mid-level
Other ways it was asked
- “How would you define the difference between the data plane and the control plane beyond just IP addresses?”
What happens when you type `ping www.google.com` into a terminal on your computer?
Asked once · last asked Feb 3 · Concept · Junior
How does the TCP/IP stack help transmit data across networks?
Asked once · last asked Feb 24 · Concept · Mid-level
What additional capabilities are needed to convert an embedded system into an IoT system?
Asked once · last asked Mar 24 · Concept · Junior
How is a TCP segment encapsulated across Layers 2, 3, and 4, and what fields are present at each layer?
Asked once · last asked Apr 13 · Concept · Junior
Ethernet, switching and wireless interview questions
Ethernet and wireless questions cover frames, fiber, VLANs, spanning tree, link aggregation, Wi-Fi, and ways to connect devices. 94 questions.
What is the difference between a VLAN and a subnet?
Asked in 2 of 337 interviews · last asked Jun 20 · Concept · Mid-level
What do you know about spanning tree—what is it for, and why is it important?
Asked in 2 of 337 interviews · last asked Apr 27 · Concept · Junior
Other ways it was asked
- “Tell me about spanning tree and why it is important.”
When an Ethernet frame arrives at a switch, what does the switch examine to decide which port to forward it through?
Asked once · last asked Jan 29 · Concept · Junior
When a device sends a frame through a new switch and the destination is unknown, what does the switch do?
Asked once · last asked Jan 29 · Scenario · Junior
How can devices in two different VLANs communicate with each other?
Asked once · last asked Jan 29 · Concept · Mid-level
Other ways it was asked
- “If the switch is Layer 2 only, how can devices in different VLANs communicate?”
What is the difference between a tagged and an untagged VLAN port?
Asked once · last asked Feb 3 · Concept · Mid-level
How could you connect a copper-only switch to a fiber network?
Asked once · last asked Feb 3 · Scenario · Mid-level
An access point has been added to a Meraki wireless controller and shows a blue LED. What does that indicate, and how would you troubleshoot it and test connectivity from a phone?
Asked once · last asked Feb 24 · Scenario · Mid-level
How do you use RF tagging and troubleshoot access points on a Cisco 9800 controller?
Asked once · last asked Feb 24 · Tooling · Mid-level
What is a major difference between pairing two Nexus switches and stacking Catalyst 3850 switches, and what underlying technology accounts for that difference?
Asked once · last asked Mar 6 · Concept · Mid-level
What does the vPC peer-switch command do on Cisco Nexus switches?
Asked once · last asked Mar 6 · Concept · Mid-level
What command do you configure under a port channel to add it to a vPC?
Asked once · last asked Mar 6 · Tooling · Mid-level
IP addressing, subnetting, DNS and DHCP interview questions
These questions cover IP addresses, subnets, gateways, ARP, NAT, DNS, and automatic address assignment. 149 questions.
What port does DNS use?
Asked in 3 of 337 interviews · last asked Oct 19 · Concept · Junior
Other ways it was asked
- “Which communication protocol does DNS use, and on which port?”
- “What is the port number of DNS?”
Why do we need IPv6 when we are currently using IPv4, and what is the difference between IPv4 and IPv6?
Asked in 2 of 337 interviews · last asked Aug 12 · Concept · Junior
Other ways it was asked
- “What's the difference between IPv4 and IPv6?”
Why does DNS use TCP in some cases instead of UDP?
Asked in 2 of 337 interviews · last asked Sep 10 · Concept · Mid-level
Other ways it was asked
- “When does DNS use TCP?”
What is the default gateway?
Asked in 2 of 337 interviews · last asked Sep 19 · Concept · Junior
Other ways it was asked
- “What is the default gateway for a network?”
Can you explain the difference between DHCP and DNS?
Asked in 2 of 337 interviews · last asked Oct 21 · Concept · Junior
Other ways it was asked
- “What is the relationship between DHCP and DNS?”
What are network and broadcast addresses in an IPv4 subnet, and what purpose does each serve?
Asked in 2 of 337 interviews · last asked May 7 · Concept · Junior
Other ways it was asked
- “What is a broadcast address in IPv4 subnetting?”
What happens when a Windows machine starts up and obtains an IP address through DHCP?
Asked once · last asked Sep 30 · Concept · Mid-level
Other ways it was asked
- “After a Windows machine obtains an IP address through DHCP, what other steps typically occur during startup?”
When you enter google.com in a browser, how does the DNS client resolve the name to an IP address?
Asked once · last asked Feb 24 · Concept · Junior
In a corporate environment, what happens when an internal DNS server cannot resolve a query?
Asked once · last asked Feb 24 · Scenario · Mid-level
When an internal DNS server cannot resolve a query, which server should it forward the query to?
Asked once · last asked Feb 24 · Concept · Mid-level
If a recursive DNS resolver cannot find an answer, where does it send the query next?
Asked once · last asked Feb 24 · Concept · Mid-level
After a DNS query reaches a top-level domain server, where does it go next?
Asked once · last asked Feb 24 · Concept · Junior
TCP and UDP interview questions
TCP and UDP questions cover ports, handshakes, protocol choices, flow control, retransmissions, error detection, and segment sizing. 41 questions.
What is a port?
Asked in 3 of 337 interviews · last asked Sep 19 · Concept · Junior
Other ways it was asked
- “What is a port number?”
What is the difference between CRC and checksum?
Asked in 2 of 337 interviews · last asked Mar 28 · Concept · Junior
What are the various types of ARQ protocols?
Asked in 2 of 337 interviews · last asked Mar 28 · Concept · Junior
What is the maximum segment size (MSS) in TCP?
Asked once · last asked Feb 24 · Concept · Junior
Why does TCP behave differently from UDP?
Asked once · last asked Feb 3 · Concept · Junior
How does TCP establish a connection?
Asked once · last asked Feb 24 · Concept · Junior
How does TCP terminate a connection?
Asked once · last asked Feb 24 · Concept · Junior
In a Wireshark capture, what does a TCP window-zero notification mean?
Asked once · last asked Mar 20 · Concept · Mid-level
What does the window size mean in a TCP packet?
Asked once · last asked Mar 20 · Concept · Junior
Which device sets the window size on a TCP connection?
Asked once · last asked Mar 20 · Concept · Junior
Which ports does PSM use to connect to target systems over RDP and SSH?
Asked once · last asked May 25 · Concept · Mid-level
How can a sliding-window mechanism be implemented with Axway Secure Transport, and is it built in or custom-developed?
Asked once · last asked Jun 18 · Concept · Senior
Routing, BGP and OSPF interview questions
Routing questions focus on route selection, policy, redistribution, convergence, multicast, MPLS, SD-WAN, and QoS. 141 questions.
What is the administrative distance of external BGP (eBGP)?
Asked in 3 of 337 interviews · last asked Apr 24 · Concept · Junior
Other ways it was asked
- “What is the administrative distance of internal BGP (iBGP)?”
- “What is the administrative distance of eBGP?”
- “What is the administrative distance for external EIGRP?”
What is the difference between static and dynamic routing?
Asked in 3 of 337 interviews · last asked Aug 4 · Concept · Junior
Other ways it was asked
- “Would you prefer static or dynamic routing?”
- “How does dynamic routing work, and when would you use it?”
What are BGP communities, and how are they used to influence routing policy?
Asked in 2 of 337 interviews · last asked Apr 7 · Concept · Mid-level
Other ways it was asked
- “What are BGP communities, and how are they used?”
How would you configure BGP to prefer a primary ISP and fail over to a secondary ISP?
Asked in 2 of 337 interviews · last asked Apr 27 · Scenario · Mid-level
Other ways it was asked
- “You have an internet router in your data center with BGP configured to AT&T and Verizon. How would you configure BGP so traffic from inside your company prefers the AT&T circuit to reach the internet, using Verizon only as a backup?”
- “How would you configure BGP on an internet router to prefer the AT&T circuit for outbound traffic, with Verizon as a backup?”
- “How would you configure BGP so inbound internet traffic prefers the Verizon circuit and uses AT&T as a backup?”
When would you choose BGP over OSPF, and what benefits does it offer?
Asked in 2 of 337 interviews · last asked Aug 4 · Scenario · Senior
Other ways it was asked
- “When would you use OSPF or BGP?”
- “When would you use BGP over OSPF, and why?”
- “What are the potential benefits of BGP compared with OSPF?”
What are the OSPF external route types E1 and E2, and what is the difference between them?
Asked in 2 of 337 interviews · last asked Apr 24 · Concept · Mid-level
Other ways it was asked
- “What is the difference between OSPF external route types E1 and E2, and which one is the default?”
If you redistribute routes between BGP and OSPF, how would you prevent routing loops, such as routes learned from OSPF being sent back into OSPF through BGP?
Asked in 2 of 337 interviews · last asked Jun 11 · Scenario · Senior
Other ways it was asked
- “When redistributing routes, how do you prevent routing loops?”
- “How can route maps be used to prevent routing loops during route redistribution?”
How does the OMP protocol work in Cisco SD-WAN?
Asked in 2 of 337 interviews · last asked Apr 24 · Concept · Mid-level
Other ways it was asked
- “What is OMP in Cisco SD-WAN, and what role does it play?”
If a router has the same /24 route learned through OSPF and BGP, which route is preferred?
Asked in 2 of 337 interviews · last asked Mar 6 · Concept · Mid-level
Other ways it was asked
- “If a router has three equal routes to 10.0.0.0/24—one learned through eBGP, one through OSPF, and one through iBGP—which route will it prefer?”
How would you improve failure detection and convergence in BGP and OSPF?
Asked in 2 of 337 interviews · last asked Aug 4 · Concept · Senior
Other ways it was asked
- “What configuration changes would you make to help BGP and OSPF detect link failures quickly?”
- “Can BGP convergence be sped up to approach OSPF convergence?”
- “How can you improve convergence and failure detection speed in OSPF or BGP?”
What is QoS, and how is it used?
Asked in 2 of 337 interviews · last asked Aug 4 · Concept · Junior
Other ways it was asked
- “What is quality of service (QoS), and when would you use it on a network?”
- “How is QoS typically implemented?”
What is OSPF?
Asked in 2 of 337 interviews · last asked Sep 17 · Concept · Junior
Other ways it was asked
- “What is OSPF, and what are its defining characteristics?”
HTTP, APIs and WebSocket interview questions
Web request questions cover HTTP methods, status codes, APIs, real-time messaging, streaming, and application protocols. 123 questions.
What is CORS, and how does it affect cross-origin requests?
Asked in 3 of 337 interviews · last asked Sep 16 · Concept · Mid-level
Other ways it was asked
- “What is CORS?”
- “What is CORS, and how does it work?”
What are WebSockets, and when would you use them?
Asked in 2 of 337 interviews · last asked Mar 5 · Concept · Mid-level
Other ways it was asked
- “What are WebSockets?”
How do HTTP/1, HTTP/2, and HTTP/3 differ at the protocol level?
Asked in 2 of 337 interviews · last asked Oct 8 · Concept · Mid-level
Other ways it was asked
- “What is the difference between HTTP/1 and HTTP/2?”
What are the components of an HTTP request?
Asked in 2 of 337 interviews · last asked Oct 8 · Concept · Junior
Other ways it was asked
- “What are the components of an HTTP response?”
- “What components are included in an HTTP POST request?”
How does a point-of-sale transaction flow from the register to the server?
Asked once · last asked Jun 8 · Design · Mid-level
Other ways it was asked
- “How does the database fit into the flow of a point-of-sale transaction from the register to the server?”
How does Kafka replicate messages to another node, and what protocol does it use?
Asked once · last asked Jul 22 · Concept · Senior
How would you extract frames from an RTSP stream for face recognition?
Asked once · last asked Sep 22 · Tooling · Mid-level
What are SFTP, FTP, HTTP, HTTPS, and SMTP used for, and how do they differ?
Asked once · last asked Feb 14 · Concept · Mid-level
How would you use socket integration to support real-time messaging in a chat application?
Asked once · last asked Feb 18 · Concept · Mid-level
If multiple websites are hosted on one server, resolve to the same IP address, and use the same port (for example, HTTPS on port 443), how does the server know which website to serve?
Asked once · last asked Mar 2 · Concept · Mid-level
If you were designing the client-server protocol yourself, for example as a browser developer, how would you make sure the server returns the website corresponding to the domain the user enters?
Asked once · last asked Mar 2 · Concept · Mid-level
What happens internally when a user clicks a URL in a browser?
Asked once · last asked Mar 10 · Concept · Junior
Network security, firewalls, VPN and TLS interview questions
Security questions cover encryption, certificates, authentication, firewall rules, VPN tunnels, remote access, and secure network design. 113 questions.
How does a browser establish a secure connection using the TLS handshake?
Asked in 3 of 337 interviews · last asked Oct 13 · Concept · Junior
Other ways it was asked
- “How does a browser establish a secure connection?”
- “How does the TLS handshake work?”
- “What do you know about the TLS handshake model?”
When a VPN user can connect but can’t reach any internal subnets, how do you distinguish routing issues from DNS issues and split-tunnel policy problems?
Asked in 2 of 337 interviews · last asked Sep 3 · Scenario · Mid-level
Other ways it was asked
- “A user connects successfully, gets an assigned VPN IP, but cannot reach any internal subnets. What would you check first regarding routes, DNS, and split tunnel versus full tunnel policy?”
What is RDP used for?
Asked in 2 of 337 interviews · last asked Sep 29 · Concept · Junior
Other ways it was asked
- “What is RDP, and what is it used for?”
What is the port number for SSH?
Asked in 2 of 337 interviews · last asked Sep 19 · Concept · Junior
Other ways it was asked
- “What port does SSH use by default?”
How do you send credentials in the HTTP Basic Authentication header?
Asked once · last asked Jul 24 · Concept · Junior
Other ways it was asked
- “How do you send credentials using HTTP Basic Authentication in an HTTP request?”
- “How do you send a username and password in the headers for HTTP Basic Authentication?”
- “How do you use HTTP Basic Authentication?”
How would you determine how many ViPNet coordinators an organization needs?
Asked once · last asked Aug 20 · Scenario · Mid-level
Other ways it was asked
- “How many ViPNet coordinators would an organization need?”
- “How does the number of employees affect the number of ViPNet coordinators an organization needs?”
What is SIP ALG (also called SIP helper), and how can it affect SIP traffic over a VPN?
Asked once · last asked Feb 17 · Concept · Mid-level
How do you configure or troubleshoot DMVPN?
Asked once · last asked Feb 24 · Tooling · Mid-level
What is the difference between DMVPN Phase 2 and Phase 3?
Asked once · last asked Feb 24 · Concept · Mid-level
How would you troubleshoot ZPA or ZIA using the Zscaler console and user logs?
Asked once · last asked Feb 24 · Tooling · Mid-level
What are the main architectural differences between Cisco ASA and Palo Alto firewalls?
Asked once · last asked Feb 27 · Concept · Mid-level
Other ways it was asked
- “What are the differences between NAT policies on Cisco ASA and Palo Alto firewalls?”
For an Internet-facing FortiGate and a new FTP server in the DMZ that must be accessible from the Internet, what questions would you ask, and how would you approach the firewall configuration?
Asked once · last asked Mar 6 · Scenario · Senior
Cloud networking, Kubernetes and load balancing interview questions
Cloud networking questions cover cloud connections, multi-cloud design, container networking, load balancing, virtualization, and data center networks such as Cisco ACI. 97 questions.
What is the difference between an Application Load Balancer, a Network Load Balancer, and a Classic Load Balancer?
Asked in 2 of 337 interviews · last asked Aug 31 · Concept · Mid-level
Other ways it was asked
- “What is the difference between an Application Load Balancer and a Network Load Balancer?”
How would you troubleshoot a Kubernetes Service that is not routing traffic to the correct pods?
Asked in 2 of 337 interviews · last asked Sep 4 · Scenario · Mid-level
Other ways it was asked
- “How do you debug a Kubernetes Service that is not reaching the correct pods?”
What is a load balancer?
Asked in 2 of 337 interviews · last asked Feb 22 · Concept · Junior
Why might a secondary AWS Direct Connect link come up briefly and then go down?
Asked once · last asked Mar 11 · Scenario · Senior
Other ways it was asked
- “How would you troubleshoot and prevent a secondary AWS Direct Connect link from repeatedly coming up and going down?”
Given a data center network to design, would you use iBGP or eBGP, and what are the reasons and benefits of your choice?
Asked once · last asked Apr 7 · Design · Senior
Other ways it was asked
- “For a data center network design, would you recommend iBGP or eBGP, and why?”
How can a container on a Docker bridge network reach the host?
Asked once · last asked Jul 16 · Concept · Junior
Other ways it was asked
- “How can a container on a Docker bridge network communicate with the host?”
What is the difference between Azure Traffic Manager and a load balancer?
Asked once · last asked Feb 9 · Concept · Mid-level
Can you explain the different Docker network types and what each one is used for?
Asked once · last asked Feb 18 · Concept · Mid-level
Other ways it was asked
- “How do the Docker network types differ, and how does communication work between the host and a container?”
What is VXLAN, and when would you use it?
Asked once · last asked Feb 19 · Concept · Mid-level
When might static routing be used with VXLAN instead of dynamic routing, and how would you evaluate whether it is the right design?
Asked once · last asked Feb 19 · Scenario · Senior
How do you decide which load-balancing method best fits a specific application?
Asked once · last asked Feb 25 · Scenario · Senior
Other ways it was asked
- “When you've implemented load balancing, how do you decide which load-balancing method best fits a specific application?”
How would you investigate and handle a load-balancer spike?
Asked once · last asked Mar 3 · Scenario · Mid-level
All 97 Cloud networking, Kubernetes and load balancing questions
Network troubleshooting, design and operations interview questions
Topics include diagnostic tools, outages, incident experience, network planning, capacity, upgrades, change control, automation, and technical work with customers. 220 questions.
How would you check and troubleshoot connectivity between two computers or servers?
Asked in 3 of 337 interviews · last asked Sep 19 · Scenario · Junior
Other ways it was asked
- “How would you test connectivity between two servers?”
- “How would you check the connection between two servers?”
- “How do you troubleshoot a connectivity issue between two computers?”
Walk me through how you would troubleshoot a network issue.
Asked in 3 of 337 interviews · last asked Aug 4 · Scenario · Mid-level
Other ways it was asked
- “How do you approach network troubleshooting?”
- “How do you troubleshoot a network issue?”
- “Walk through how you would troubleshoot a major network issue.”
Tell me about a time you handled a significant network event. What happened, what steps did you take, and what tools or applications did you use to identify and resolve the problem?
Asked in 2 of 337 interviews · last asked Apr 23 · Behavioral · Mid-level
Other ways it was asked
- “Tell me about a time you responded to a Level 1 or Level 2 incident or network outage. What was the issue, and how did you resolve it?”
What command would you use in Linux to list the ports listening on a server?
Asked in 2 of 337 interviews · last asked Jul 30 · Tooling · Junior
Other ways it was asked
- “How can you check which ports a server is listening on?”
A user cannot connect to the company Wi-Fi, but other users can. How would you troubleshoot the issue step by step?
Asked in 2 of 337 interviews · last asked Aug 9 · Scenario · Mid-level
Other ways it was asked
- “How would you troubleshoot a user who cannot connect to Wi‑Fi?”
How would you identify the cause of a technical issue involving DHCP?
Asked once · last asked Feb 25 · Scenario · Mid-level
Other ways it was asked
- “How would you resolve a technical issue involving DHCP?”
What information do you generally need from networking teams when you are starting a project?
Asked once · last asked Oct 6 · Scenario · Mid-level
Other ways it was asked
- “What challenges do you face when gathering information from networking teams at the start of a project?”
How do you filter Wireshark traffic by source or destination IP address?
Asked once · last asked Oct 16 · Tooling · Junior
How would you troubleshoot a down fiber connection between two routers in the same room, where the connection runs from an optic to a patch panel, through structured fiber to another patch panel, and then to the other router?
Asked once · last asked Feb 3 · Scenario · Mid-level
How would you troubleshoot a machine connected to a switch port with an assigned VLAN that does not get an IP address dynamically, but works and communicates when configured with a static IP?
Asked once · last asked Feb 3 · Scenario · Mid-level
How would you design a network for a doctor's office with up to 100 client devices, 10 servers, a secure remote connection to the hospital, and wireless guest access to the internet but not the intranet?
Asked once · last asked Feb 3 · Design · Senior
If your application is running in production but cannot reach a database resource, how would you investigate the problem and identify its root cause?
Asked once · last asked Feb 9 · Scenario · Senior
All 220 Network troubleshooting, design and operations questions
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How this list is made
Every question here was asked by a real interviewer in a real job interview that a candidate ran MeetAssist in. After the call, the interviewer's questions are pulled from the transcript. Practice sessions, tests, exams and anything that was not a job interview are dropped.
Questions are rewritten so they make sense on their own: names of people, employers and clients are removed, and speech-to-text mistakes are fixed. Small talk, logistics and questions about one candidate's own résumé are left out. Rephrasings of the same question are merged, and the count is the number of different interviews it came up in.
The interviews come from candidates who use MeetAssist, so they lean towards software, data and AI roles: the shares describe these interviews, not every Computer Networks interview. Answers to the most asked questions are written and checked by an editor; a "common mistake" is shown only when reviews of real answers in these interviews show it, with the count.
337 interviews, 208 candidates, Nov 2025 to Oct 2026. Updated every month with new interviews.
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