Network Engineer Interview Questions and Answers, Networking has become a popular career option for many with the increased usage of computers and the internet. While appearing in the interview for the position of network administrator, be prepared to answer technical questions. Our detailed guide on networking interview questions and answers covers the most frequently asked questions in the interview.
What are the different types of networks?
Ans. Considering the size or span of a network, we can classify them as follows:
PAN (Personal Area Network) – PAN is made up of devices used by a single person. It has a range of a few meters.
WPAN (Wireless Personal Area Network) – It is a PAN network that uses wireless technologies as a medium.
LAN (Local Area Network) – LAN is a network whose range is limited to a relatively small area, such as a room, a building, an airplane, etc.
WLAN (Wireless Local Area Network) – WLAN is a LAN network that uses wireless means of communication. It is a widely used configuration due to its scalability and because it does not require the installation of cables.
CAN (Campus Area Network) – A network of high-speed devices that connects LANs in a limited geographical area, such as a university campus, a military base, etc.
MAN (Metropolitan Area Network) or metropolitan area network – It is a high-speed (broadband) network providing coverage in a larger geographic area than a campus, but still limited.
WAN (Wide Area Network) – WAN extends over a large geographical area using unusual means of communication, such as satellites, interoceanic cables, fiber optics, etc. Use public media.
VLAN – It is a type of logical or virtual LAN, mounted on a physical network, in order to increase security and performance. In special cases, thanks to the 802.11Q protocol (also called QinQ), it is possible to mount virtual networks on WAN networks. It is important not to confuse this implementation with VPN technology.
Network Engineer Basic Interview Questions and Answers
1) What is a LAN?
LAN is short for Local Area Network. It refers to the connection between computers and other network devices that are located within a small physical location.
2) What is the difference between a normal LAN cable and a cross cable? What could be the maximum length of the LAN cable?
The way the paired wires are connected to the connector (RJ45) is different in cross cable and normal LAN cable.
The theoretical length is 100 meters but after 80 meters you may see a drop in speed due to loss of signal.
3) What is DHCP? Why it is used? What are scopes and super scopes?
DHCP: Dynamic host configuration protocol. It is used to allocate IP addresses to a large number of PCs in a network environment. Which makes IP management very easy.
Scope: Scope contains IP addresses like subnet mask, gateway IP, DNS server IP and exclusion range which a client can use to communicate with the other PCs in the network.
Superscope: When we combine two or more scopes together it's called superscope.
4) What are the types of LAN cables used? What is a cross cable?
Types of LAN cables that are in use are “Cat 5” and “Cat 6”. “Cat 5” can support 100 Mbps of speed and “CAT 6” can support 1Gbps of speed.
Cross cable: It is used to connect the same type of devices without using a switch/hub so that they can communicate.
5) What is Active Directory?
A central component of the Windows platform, the Active Directory directory service provides the means to manage the identities and relationships that make up network environments. For example, we can create, manage, and administrator users, computers, and printers in the network from an active directory.
6) What is DNS? Why it is used? What are “forward lookup” and “reverse lookup” in DNS? What are A records and MX records?
DNS is a domain naming service and is used for resolving names to IP addresses and IP addresses to names. The computer understands only numbers while we can easily remember names. So to make it easier for us what we do is we assign names to computers and websites. When we use these names (Like yahoo.com) the computer uses
DNS to convert to IP address (number) and it executes our request.
Forward lookup: Converting names to IP addresses is called forward lookup.
Reverse lookup: Resolving IP addresses to names is called reverse lookup.
‘A’ record: It's called host record and it has the mapping of a name to an IP address. This is the record in DNS with the help of which DNS can find out the IP address of a name.
‘MX’ Record: it's called mail exchanger record. It's the record needed to locate the mail servers in the network. This record is also found in DNS.
7) What is the IPCONFIG command? Why it is used?
IPCONFIG command is used to display the IP information assigned to a computer. From the output, we can find out the IP address, DNS IP address, gateway IP address assigned to that computer.
8) What is the APIPA IP address? Or what IP address is assigned to the computer when the DHCP server is not available?
When the DHCP server is not available the Windows client computer assigns an automatic IP address to itself so that it can communicate with the network computers. This IP address is called APIPA. ITs in the range of 169.254.X.X.
APIPA stands for Automatic private IP addressing. It's in the range of 169.254.X.X.
9) What is a DOMAIN? What is the difference between a domain and a workgroup?
The domain is created when we install Active Directory. It’s a security boundary that is used to manage computers inside the boundary. A domain can be used to centrally administer computers and we can govern them using common policies called group policies.
We can’t do the same with workgroups.
10) Do you know how to configure outlook 2000 and outlook 2003 for a user?
Please visit the link below to find out how to configure outlook 2000 and outlook 2003.http://www.it.cmich.edu/quickguides/qg_outlook2003_server.asp
11) What is a PST file and what is the difference between a PST file and OST file? What file is used by outlook express?
PST file is used to store the mails locally when using outlook 2000 or 2003. OST file is used when we use outlook in cached exchanged mode. Outlook expresses users' odb file.
12) What is BSOD? What do you do when you get a blue screen on a computer? How do you troubleshoot it?
BSOD stands for the blue screen of Death. when there is a hardware or OS fault due to which the windows OS can run it give a blue screen with a code. The best way to resolve it is to boot the computer is “LAst known good configuration”. If this doesn’t work then boot the computer in safe mode. If it boots up then the problem is with one of the devices or drivers.
13) What is RIS? What is Imaging/ghosting?
RIS stands for remote installation services. You save the installed image on a windows server and then we use RIS to install the configured on in the new hardware. We can use it to deploy both server and client OS. Imaging or ghosting also does the same job of capturing an installed image and then installing it on new hardware when there is a need. We go for RIS or imaging/ghosting because installing OS every time using a CD can be a very time-consuming task. So to save that time we can go for RIS/Ghosting/imaging.
14) What is VPN and how to configure it?
VPN stands for Virtual private network. VPN is used to connect to the corporate network to access the resources like mail and files in the LAN. VPN can be configured using the steps mentioned in the KB: http://support.microsoft.com/kb/305550
15) Your computer slowly drops out of network. A reboot of the computer fixes the problem. What to do to resolve this issue?
Update the network card driver.
16) Your system is infected with Virus? How to recover the data?
Install another system. Install the OS with the latest patches, Antivirus with the latest updates. Connect the infected HDD as a secondary drive in the system. Once done scan and clean the secondary HDD. Once done copy the files to the new system.
17) 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.
18) What is the difference between a switch and a hub?
Switch sends the traffic to the port for which it's meant. Hub sends the traffic to all the ports.
19) What is a router? Why do we use it?
The router is a switch that uses routing protocols to process and send the traffic. It also receives the traffic and sends it across but it uses the routing protocols to do so.
20) What are manageable and nonmanageable switches?
Switches that can be administered are calledmanageable switches. For example, we can create a VLAN for such a switch. On no manageable switches, we can’t do so.
21) What is NIC?
A network card, network adapter, or NIC (network interface controller) is a piece of computer hardware designed to allow computers to communicate over a computer network
22) What is a USB?
Universal Serial Bus (USB) is a serial bus standard to interface devices. Devices like Modem, Mouse, Keyboard, etc can be connected.
23) Dialup vs. Broadband
A broadband connection (ADSL) provides high-speed Internet access over a standard phone line. The advantage of a broadband connection over a standard dial-up service is that the Broadband is considerably faster, and is “always-on”, meaning that once you”re-logged on, your PC is online until the PC is turned off again.
Broadband offers high-speed Internet access and allows telephone calls and a permanent Internet connection to share a single phone line simultaneously whereas in a dial-up connection either an Internet connection or a telephone call can be made at a given time.
24) LAN and WAN
A local area network is a computer network covering a small geographic area, like a home, office, or group of buildings
A Wide Area Network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries). Or, less formally, a network that uses routers and public communications links
25) Microsoft Access
Microsoft Office Access, previously known as Microsoft Access, is a relational database management system from Microsoft.
26) What is RAS?
Remote Access Services (RAS) 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.
27) Difference between Client Mail and WebMail?
Email clients download your emails onto your computer. Using a specialized email program such as Outlook Express or Apple Mail has the advantage of giving you complete control over your email; every email you receive is placed on your computer and you can keep as many large file attachments as you want.
Checking your email through our webmail is similar to using Hotmail or Yahoo! Mail. You never actually copy your messages to your computer; in fact, you are looking at them through your web browser on somebody else”s computer. When you are not online, you are not able to see your email.
28) RAM and ROM
random access memory, a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. RAM is the most common type of memory found in computers and other devices, such as printers.
Pronounced Rahm, an acronym for read-only memory, computer memory on which data has been prerecorded. Once data has been written onto a ROM chip, it cannot be removed and can only be read. Unlike main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile.
29) Spamguard
Spam Guard is an Outlook add-in that filters email that arrives in your inbox. If the sender of any message cannot be identified then the message is moved into a spam quarantine folder. Messages deposited in the spam quarantine folder can be inspected and either deleted or approved at your leisure.
30) Firewall and Antivirus
A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.
Antivirus is a software program that helps protect a computer against being infected by a virus.
31) DNS
Short for Domain Name System (or Service or Server), an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they”re easier to remember. The Internet, however, is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to 198.105.232.4.
32) IPConfig - IPConfig is a command-line tool used to control the network connections on Windows NT/2000/XP machines. There are three main commands: “all”, “release”, and “renew”. IPConfig displays all current TCP/IP network configuration values and refreshes Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) settings. Used without parameters, IPConfig displays the IP address, subnet mask, and default gateway for all adapters.
33) Traceroute
Traceroute is the program that shows you the route over the network between two systems, listing all the intermediate routers a connection must pass through to get to its destination. It can help you determine why your connections to a given server might be poor, and can often help you figure out where exactly the problem is. It also shows you how systems are connected to each other, letting you see how your ISP connects to the Internet as well as how the target system is connected.
34) What is the equivalent layer or layers of the TCP/IP Application layer in terms of OSI reference model?
The TCP/IP Application layer actually has three counterparts on the OSI model: the Session layer, Presentation Layer and Application Layer.
35) 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.
36) 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.
37) What are firewalls?
Ans. A firewall is a network security system, responsible to manage network traffic. It uses a set of security rules to prevent remote access and content filtering. Firewalls are used to protect the systems or networks from viruses, worms, malware, etc. Firewalls are usually of two types –
Physical – A physical firewall or hardware firewall is a physical device, sits between the external network and the server. They analyze incoming traffic and filter out any threats to the device. Widely used in institutions and large companies.
Logical – A logical or software firewall can exist anywhere on the subnet and protects hosts anywhere on the subnet without rewiring. They only protect the computer on which they are installed, and in many cases, they are integrated into the operating system itself.
38) Describe star topology
Star topology consists of a central hub that connects to nodes. This is one of the easiest to setup and maintain.
39) What are gateways?
Gateways provide connectivity between two or more network segments. It is usually a computer that runs the gateway software and provides translation services. This translation is key in allowing different systems to communicate on the network.
40) What is the disadvantage of a star topology?
One major disadvantage of star topology is that once the central hub or switch gets damaged, the entire network becomes unusable.
41) What is SLIP?
SLIP, or Serial Line Interface Protocol, is actually an old protocol developed during the early UNIX days. This is one of the protocols that are used for remote access.
42) Give some examples of private network addresses.
- 10.0.0.0 with a subnet mask of 255.0.0.0
- 172.16.0.0 with subnet mask of 255.240.0.0
- 192.168.0.0 with subnet mask of 255.255.0.0+
43) What is tracert?
Tracert is a Windows utility program that can be 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.
44) What are the functions of a network administrator?
A network administrator has many responsibilities that can be summarized into 3 key functions: installation of a network, the configuration of network settings, and maintenance/troubleshooting of networks.
45) Describe at one disadvantage of a peer-to-peer network.
When you are accessing the resources that are shared by one of the workstations on the network, that workstation takes a performance hit.
46) What is Hybrid Network?
A hybrid network is a network setup that makes use of both client-server and peer-to-peer architecture.
47) 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.
48) What is the main job of the ARP?
The main task of ARP or Address Resolution Protocol is to map a known IP address to a MAC layer address.
49) What is TCP/IP?
TCP/IP is short for Transmission Control Protocol / Internet Protocol. This is a set of protocol layers that is designed to make data exchange possible on different types of computer networks, also known as heterogeneous networks.
50) How can you manage a network using a router?
Routers have a built-in console that lets you configure different settings, like security and data logging. You can assign restrictions to computers, such as what resources it is allowed access or what particular time of the day they can browse the internet. You can even put restrictions on what websites are not viewable across the entire network.
51) What protocol can be applied when you want to transfer files between different platforms, such as between UNIX systems and Windows servers?
Use FTP (File Transfer Protocol) for file transfers between such different servers. This is possible because FTP is platform-independent.
52) What is the use of a default gateway?
Default gateways provide means for the local networks to connect to the external network. The default gateway for connecting to the external network is usually the address of the external router port.
53) One way of securing a network is through the use of passwords. What can be considered good passwords?
Good passwords are made up of not just letters, but by combining letters and numbers. A password that combines uppercase and lowercase letters is more favorable than one that uses all upper case or all lower case letters. Passwords must be not words that can easily be guessed by hackers, such as dates, names, favorites, etc. Longer passwords are also better than short ones.
54) What is the proper termination rate for UTP cables?
The proper termination for unshielded twisted pair network cable is 100 ohms.
55) What is netstat?
Netstat is a command-line utility program. It provides useful information about the current TCP/IP settings of a connection.
56) What is the number of network IDs in a Class C network?
For a Class C network, the number of usable Network ID bits is 21. The number of possible network IDs is 2 raised to 21 or 2,097,152. The number of host IDs per network ID is 2 raised to 8 minus 2, or 254.
57) What happens when you use cables longer than the prescribed length?
Cables that are too long would result in signal loss. This means that data transmission and reception would be affected because the signal degrades over length.
58) What common software problems can lead to network defects?
Software related problems can be any or a combination of the following:
- client-server problems
- application conflicts
- error in configuration
- protocol mismatch
- security issues
- user policy and rights issues
59) What is ICMP?
ICMP is Internet Control Message Protocol. It provides messaging and communication for protocols within the TCP/IP stack. This is also the protocol that manages error messages that are used by network tools such as PING.
60) What is Ping?
Ping is a utility program that allows you to check connectivity between network devices on the network. You can ping a device by using its IP address or device name, such as a computer name.
61) What is peer to peer?
Peer peers are networks that do not rely on a server. All PCs on this network act as individual workstations.
62) What is DNS?
DNS is a Domain Name System. The main function of this network service is to provide host names to TCP/IP address resolution.
63) 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.
64) What is the difference between a hub and a switch?
A hub acts as a multiport repeater. However, as more and more devices connect to it, it would not be able to efficiently manage the volume of traffic that passes through it. A switch provides a better alternative that can improve the performance especially when high traffic volume is expected across all ports.
65) What are the different network protocols that are supported by Windows RRAS services?
There are three main network protocols supported: NetBEUI, TCP/IP, and IPX.
66) What are the maximum networks and hosts in class A, B, and C networks?
- For Class A, there are 126 possible networks and 16,777,214 hosts
- For Class B, there are 16,384 possible networks and 65,534 hosts
- For Class C, there are 2,097,152 possible networks and 254 hosts
67) What is the standard color sequence of a straight-through cable?
orange/white, orange, green/white, blue, blue/white, green, brown/white, brown.
68) What protocols fall under the Application layer of the TCP/IP stack?
The following are the protocols under the TCP/IP Application layer: FTP, TFTP, Telnet, and SMTP.
69) You need to connect two computers for file sharing. Is it possible to do this without using a hub or router?
Yes, you can connect two computers together using only one cable. A crossover-type cable can be used in this scenario. In this setup, the data transmit pin of one cable is connected to the data receive pin of the other cable and vice versa.
70) 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.
71) What is the difference between a straight-through and crossover cable?
A straight-through cable is used to connect computers to a switch, hub, or router. A crossover cable is used to connect two similar devices together, such as a PC to PC or Hub to the hub.
72) What is client/server?
Client/server is a type of network wherein one or more computers act as servers. Servers provide a centralized repository of resources such as printers and files. Clients refer to the workstation that accesses the server.
73) Describe networking.
Networking refers to the interconnection between computers and peripherals for data communication. Networking can be done using wired cabling or through a wireless link.
74) 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 replaced by another one.
75) Define clustering support
Clustering support refers to the ability of a network operating system to connect multiple servers in a fault-tolerant group. The main purpose of this is that in the event that one server fails, all processing will continue with the next server in the cluster.
76) In a network that contains two servers and twenty workstations, where is the best place to install an Anti-virus program?
An anti-virus program must be installed on all servers and workstations to ensure protection. That’s because individual users can access any workstation and introduce a computer virus when plugging in their removable hard drives or flash drives.
77) 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.
78) 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.
79) 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.
80) What is SMTP?
SMTP is short for Simple Mail Transfer Protocol. This protocol deals with all Internal mail and provides the necessary mail delivery services on the TCP/IP protocol stack.
81) What is multicast routing?
Multicast routing is a targeted form of broadcasting that sends messages to a selected group of users, instead of sending them to all users on a subnet.
82) 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 ensures that information that is intercepted halfway would remain unreadable because the user has to have the correct password or key for it.
83) How are IP addresses arranged and displayed?
IP addresses are displayed as a series of four decimal numbers that are separated by period or dots. Another term for this arrangement is the dotted-decimal format. An example is 192.168.101.2
84) Explain the importance of authentication.
Authentication is the process of verifying a user’s credentials before he can log into the network. It is normally performed using a username and password. This provides a secure means of limiting access from unwanted intruders on the network.
85) 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.
86) What are the different technologies involved in establishing WAN links?
Analog connections – using conventional telephone lines; Digital connections – using digital-grade telephone lines; switched connections – using multiple sets of links between sender and receiver to move data.
87) What is one advantage of mesh topology?
In the event that one link fails, there will always be another available. Mesh topology is actually one of the most fault-tolerant network topologies.
88) When troubleshooting computer network problems, what common hardware-related problems can occur?
A large percentage of a network is made up of hardware. Problems in these areas can range from malfunctioning hard drives, broken NICs, and even hardware startups. Incorrect hardware configuration is also one of those culprits to look into.
89) What can be done to fix signal attenuation problems?
A common way of dealing with such a problem is to use repeaters and hubs because it will help regenerate the signal and therefore prevent signal loss. Checking if cables are properly terminated is also a must.
90) 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.
91) Explain profile in terms of networking concept?
Profiles are the configuration settings made for each user. A profile may be created that puts a user in a group, for example.
92) 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.
93) What is the role of IEEE in computer networking?
IEEE, or the Institute of Electrical and Electronics Engineers, is an organization composed of engineers that issues and manages standards for electrical and electronic devices. This includes networking devices, network interfaces, cablings, and connectors.
94) What protocols fall under the TCP/IP Internet Layer?
There are 4 protocols that are being managed by this layer. These are ICMP, IGMP, IP, and ARP.
95) When it comes to networking, what are rights?
Rights refer to the authorized permission to perform specific actions on the network. Each user on the network can be assigned individual rights, depending on what must be allowed for that user.
96) What is one basic requirement for establishing VLANs?
A VLAN is required because at the switch level there is only one broadcast domain, it means whenever a new user is connected to the switch this information is spread throughout the network. VLAN on switch helps to create separate broadcast domains at the switch level. It is used for security purposes.
97) What is IPv6?
IPv6, or Internet Protocol version 6, was developed to replace IPv4. At present, IPv4 is being used to control internet traffic but is expected to get saturated in the near future. IPv6 was designed to overcome this limitation.
98) What is the RSA algorithm?
RSA is short for the Rivest-Shamir-Adleman algorithm. It is the most commonly used public-key encryption algorithm in use today.
99) What is mesh topology?
Mesh topology is a setup wherein each device is connected directly to every other device on the network. Consequently, it requires that each device have at least two network connections.
100) what is the maximum segment length of a 100Base-FX network?
The maximum allowable length for a network segment using 100Base-FX is 412 meters. The maximum length for the entire network is 5 kilometers