Network Engineer Interview Questions And Answers

Q1. What is a ‘link’?
A link refers to the connectivity between two devices. It includes the type of cables and protocols used in order for one device to be able to communicate with the other.

Q2. What is a ‘backbone network’?
A backbone network is a centralised infrastructure that is designed to distribute different routes and data to various networks. It also handles management of bandwidth and various channels.

Q3. What is DNS? Why is it used?
DNS (Domain Name System) is a central part of the Internet, providing a way to match names (a website you’re seeking) to numbers (the address for the website).

Q4. What is a LAN?
A LAN (Local Area Network) and refers to the connection between computers and other network devices that are located within a small physical location.

Q5. What is a WAN?
A wide area network (WAN) is a telecommunications network or computer network that extends over a large geographical distance.

Q6. What is ‘network topology’?
 Network topology refers to the layout of a computer network. It shows how devices and cables are physically laid out, as well as how they connect to one another.

Q7. What is a router? What are its basic roles?
A router is a layer 3 network device used to establish communication between different networks. The roles of a router are –

• inter-network communication
• Best path selection
• Packet forwarding
• Packet filtering

Q8. What are the types of LAN cables used?
There are two types of LAN cables used – ‘Cat 5’ and ‘Cat 6.’ Cat 5 can support 100Mbps of speed while Cat 6 can support 1Gbps of speed

Q9. What is a ‘cross table’?
This is a type of connection between same types of devices without using a hub/switch so that they can communicate.

Q10. What is point to point link?
It refers to a direct connection between two computers on a network. A point to point connection does not need any other network devices other than connecting a cable to the NIC cards of both computers.

Q11. What is subnet mask?
A subnet mask is combined with an IP address in order to identify two parts: the extended network address and the host address. Like an IP address, a subnet mask is made up of 32 bits.

Q12. A gateway works in which layer of the OSI model?
Transport layer.

Q13. How many layers are there in the OSI reference model? Name them
There are 7 layers: physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer.

Q14. Differentiate between ‘forward lookup’ and ‘reverse lookup’ in DNS?
Converting names to IP addresses is called forward lookup.
Resolving IP addresses to names is called reverse lookup.

Q15. What is RIP?
RIP (Routing Information Protocol) is used by routers to send data from one network to another.

Q16. What are ‘firewalls’?
Firewalls serve to protect an internal network from external attacks

Q17. What are the criteria for the best path selection of a router?
The following parameters define the path selection:

• Longest prefix match
• Minimum AD (administrative distance)
• Lowest metric value

Q18. Define ‘anonymous FTP’.
Anonymous FTP is a way of granting a user access to files in public servers.

Q19. What is the difference between ‘standard’ and ‘extended’ ACL (access control list)?
Standard ACLs are source-based, whereas extended ACLs are source- and destination-based.

Q20. What is RAS?
RAS (Remote Access Services) refers to any combination of hardware and software to enable remote access to tools or information that typically reside on a network of IT devices.

Q21. What is NIC?
NIC (Network Interface Card) is a peripheral card that is attached to a PC in order to connect to a network. Every NIC has its own MAC address that identifies the PC on the network

Q22. How many layers are there under TCP/IP?
There are four layers: the Network Layer, Internet Layer, Transport Layer and Application Layer.

 Q23. What are different ways of securing a computer network?
There are several ways to do this. Install reliable and updated anti-virus program on all computers. Make sure firewalls are setup and configured properly. User authentication will also help a lot. All of these combined would make a highly secured network.

Q24. What does 10Base-T mean?
The 10 refers to the data transfer rate, in this case is 10Mbps. The word Base refers to base band, as oppose to broad band. T means twisted pair, which is the cable used for that network.

Q25. What is the maximum length allowed for a UTP cable?
A single segment of UTP cable has an allowable length of 90 to 100 meters. This limitation can be overcome by using repeaters and switches.

Q26. What is data encapsulation?
Data encapsulation is the process of breaking down information into smaller manageable chunks before it is transmitted across the network. It is also in this process that the source and destination addresses are attached into the headers, along with parity checks.

Q27. Describe Network Topology
Network Topology refers to the layout of a computer network. It shows how devices and cables are physically laid out, as well as how they connect to one another.

Q28. What is VPN?
VPN means Virtual Private Network, a technology that allows a secure tunnel to be created across a network such as the Internet. For example, VPNs allow you to establish a secure dial-up connection to a remote server.

Q29. Briefly describe NAT.
NAT is Network Address Translation. This is a protocol that provides a way for multiple computers on a common network to share single connection to the Internet.

Q30. What is a private IP address?
Private IP addresses are assigned for use on intranets. These addresses are used for internal networks and are not routable on external public networks. These ensures that no conflicts are present among internal networks while at the same time the same range of private IP addresses are reusable for multiple intranets since they do not “see” each other.

Q31.  What is the main purpose of OSPF?
OSPF, or Open Shortest Path First, is a link-state routing protocol that uses routing tables to determine the best possible path for data exchange.

Q32. What is NOS?
NOS, or Network Operating System, is specialized software whose main task is to provide network connectivity to a computer in order for it to be able to communicate with other computers and connected devices.

Q33. What is tracert?
Tracert is a Windows utility program that can used to trace the route taken by data from the router to the destination network. It also shows the number of hops taken during the entire transmission route.

Q34. What is Hybrid Network?
A hybrid network is a network setup that makes use of both client-server and peer-to-peer architecture.

Q35. What is DoS?
DoS, or Denial-of-Service attack, is an attempt to prevent users from being able to access the internet or any other network services. Such attacks may come in different forms and are done by a group of perpetuators. One common method of doing this is to overload the system server so it cannot anymore process legitimate traffic and will be forced to reset.

Q36. What is the purpose of cables being shielded and having twisted pairs?
The main purpose of this is to prevent crosstalk. Crosstalks are electromagnetic interferences or noise that can affect data being transmitted across cables.

Q37. What is the advantage of address sharing?
By using address translation instead of routing, address sharing provides an inherent security benefit. That’s because host PCs on the Internet can only see the public IP address of the external interface on the computer that provides address translation and not the private IP addresses on the internal network.

Q38. What are MAC addresses?
MAC, or Media Access Control, uniquely identifies a device on the network. It is also known as physical address or Ethernet address. A MAC address is made up of 6-byte parts.

Q39. How can you identify the IP class of a given IP address?
By looking at the first octet of any given IP address, you can identify whether it’s Class A, B or C. If the first octet begins with a 0 bit, that address is Class A. If it begins with bits 10 then that address is a Class B address. If it begins with 110, then it’s a Class C network.

Q40. What do mean by tunnel mode?
This is a mode of data exchange wherein two communicating computers do not use IPSec themselves. Instead, the gateway that is connecting their LANs to the transit network creates a virtual tunnel that uses the IPSec protocol to secure all communication that passes through it.

Q41. What is DHCP?
DHCP is short for Dynamic Host Configuration Protocol. Its main task is to automatically assign an IP address to devices across the network. It first checks for the next available address not yet taken by any device, then assigns this to a network device.

Q42. What advantages does fiber optics have over other media?
One major advantage of fiber optics is that is it less susceptible to electrical interference. It also supports higher bandwidth, meaning more data can be transmitted and received. Signal degrading is also very minimal over long distances.

Q43. What is ipconfig?
Ipconfig is a utility program that is commonly used to identify the addresses information of a computer on a network. It can show the physical address as well as the IP address.

Q44. Describe Ethernet.
Ethernet is one of the popular networking technologies used these days. It was developed during the early 1970s and is based on specifications as stated in the IEEE. Ethernet is used in local area networks.

Q45.  What are some drawbacks of implementing a ring topology?
In case one workstation on the network suffers a malfunction, it can bring down the entire network. Another drawback is that when there are adjustments and reconfigurations needed to be performed on a particular part of the network, the entire network has to be temporarily brought down as well.

Q46. How does dynamic host configuration protocol aid in network administration?
Instead of having to visit each client computer to configure a static IP address, the network administrator can apply dynamic host configuration protocol to create a pool of IP addresses known as scopes that can be dynamically assigned to clients.

Q47. What is sneakernet?
Sneakernet is believed to be the earliest form of networking wherein data is physically transported using removable media, such as disk, tapes.

Q48. When you move the NIC cards from one PC to another PC, does the MAC address gets transferred as well?
Yes, that’s because MAC addresses are hard-wired into the NIC circuitry, not the PC. This also means that a PC can have a different MAC address when the NIC card was replace by another one.

Q49. What is the importance of Encryption on a network?
Encryption is the process of translating information into a code that is unreadable by the user. It is then translated back or decrypted back to its normal readable format using a secret key or password. Encryption help ensure that information that is intercepted halfway would remain unreadable because the user has to have the correct password or key for it.

Q50. What is the difference between CSMA/CD and CSMA/CA?
CSMA/CD, or Collision Detect, retransmits data frames whenever a collision occurred. CSMA/CA, or Collision Avoidance, will first broadcast intent to send prior to data transmission.