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Prepare Your Answers for 15 Server and Networking Interview Questions

Like every other industry, the technology sector has been blindsided by the coronavirus pandemic of 2020. But unlike many sectors, these changes may eventually even yield some benefits to the tech industry.

Given this, I thought it would be a good time to compile some of the most common questions applicants face when interviewing for server and networking jobs. As you can imagine, the requirements vary widely. But knowing the answers to these 15 questions is a must. Even if you think you know the answer, it can be tricky to provide that answer in a succinct, clear manner.

There is some overlap, but for simplicity's sake, we've divided these questions into three categories: servers, systems design and networking.

Server-Specific Questions

1. What Is Windows Server?

Microsoft Windows Server is an enterprise-class operating system. It is designed to share services with multiple users and provide extensive administrative control of data storage, apps and corporate networks. It's been around in one form or another since the early 1980s when Microsoft produced two operating system lines: MS-DOS and Windows NT. Symmetric multiprocessing, which makes applications run faster on machines with several processors, is a feature in the NT architecture.

Later iterations of Windows Server can be deployed either on-premises or on a cloud platform, such as Microsoft Azure. Key features in later versions of Windows Server include:

  • Active Directory: Automates the management of user data, security and distributed resources, and enables interoperation with other directories
  • Server Manager: A utility to administer server roles and make configuration changes to local or remote machines.

If you're being asked this question, you'll likely be expected to show proficiency with current versions of Windows Server 2016 and 2019, Microsoft VMM 2019 and SQL Server with PowerShell. You might also be expected to support Active Directory, Exchange, SQL Server, SharePoint, Office 365, Azure, Citrix and Hyper-V.

2. What Are Proxy Servers and Why Are They Important?

A proxy server is a dedicated computer (or a software system running on a computer) that acts as an intermediary between an endpoint device, such as a computer, and another server from which a user or client is requesting a service.

To the user, the proxy server is invisible; all internet requests and returned responses appear to be directly with the addressed internet server.

Proxy servers are used for both legal and illegal purposes. Legitimate purposes include facilitating security, providing administrative control or providing caching services. Illegitimate purposes include monitoring traffic to undermine user privacy. An advantage of a proxy server is that its cache can serve all users. If one or more internet sites are frequently requested, these are likely to be in the proxy's cache, which improves user response time. A proxy can also log its interactions, which can be helpful for troubleshooting. 

3. How Would You Recover Lost Files From a System Infected by a Virus?

If you're asked this question, know that the interviewer has had some firsthand experience. When you give your response, it's OK to explain what you would have done to avoid the loss in the first place -- as long as you don't sound condescending.

Explain that the data recovery would depend on a number of circumstances, including which virus was the culprit. The recovery would also be limited by the data recovery software used to create the backup and the backup target media.

Communicate that you would need to determine whether the actual files were corrupt or just the reference files, such as the file allocation table that Windows uses, to track which files are on the hard drive and where they are stored.

Also, note what you would do to retrieve files that were not backed up and accidentally deleted from a computer's file system -- knowing that they likely still remain on the hard disk in fragments.

If you've used specific recovery tools or third-party services, now is a good time to mention that.

4. What's the Difference Between a Firewall and an Antivirus?

Firewalls and antivirus software are typically used in tandem to protect data and access to the servers in which they reside.

Firewall software prevents intruders from gaining unauthorized access to a private network, and ultimately, the servers. They do this by establishing a border between an external network and the network they guard. The firewall inspects all packets entering and leaving the guarded network. As it inspects, it uses a set of preconfigured rules to distinguish between benign and malicious packets.

Conversely, antivirus protects the data and servers from malware, such as viruses and worms. Antivirus software typically runs in the background, scanning servers and other network devices to detect and restrict the spread of malware. Many antivirus software programs include real-time threat detection and protection to guard against potential vulnerabilities as they happen, as well as system scans that monitor device and system files looking for possible risks.

5. What's the Difference Between Tomcat and the Apache Web Server?

Purpose.

The purpose of the Apache HTTP Server is to simply serve static files such as text, HTML, images, audio and video files to web-based clients.

In contrast, the Apache Tomcat server delivers content that changes. These changes depend on who the client is, whether the client has signed in and what the client has done on previous interactions with the server.

Another key difference is the prerequisites. The Apache HTTP Server has no prerequisites. It can be installed on any computer that runs a modern edition of Windows, a Linux distribution or Unix. Tomcat, however, requires a JDK installation, along with a properly configured JAVA_HOME environment variable. The dynamic nature of Apache Tomcat comes from logic implemented in Java code that is written and deployed to it.

6. What Professional Server Certifications Do You Have?

This is about as point-blank as it gets. Here, your interviewer wants to know if you've picked up relevant certifications such as Microsoft Certified Solutions Expert (MCSE) Core Infrastructure or Productivity certifications, VMware Certified Professional (VCP), or others.

In 2019, Microsoft announced plans to retire several server certifications in favor of role-based certifications for Azure. Therefore, you should prepare to explain how your certifications are still applicable to the job, as there are still vast numbers of on-premises Windows Server deployments in enterprises.

7. What Role Do Servers Typically Play in IT Monitoring?

IT monitoring covers three sections: the foundation, software and interpretation.

Servers are included in the foundation, which is the lowest layer of a software stack. The foundation also includes CPUs and VMs.

IT monitoring can rely on agents or be agentless. Agents are independent programs installed on the monitored device to collect hardware or software performance data, reporting it to a management server. Agentless monitoring uses existing communication protocols to emulate an agent with many of the same functionalities.

For example, to monitor server use, an IT admin installs an agent on the server. A management server receives that data from the agent and displays it to the user via the IT monitoring software interface, often as a graph of performance over time. If the server stops working as intended, the tool alerts the administrator, who can repair, update or replace the item until it meets the standard for operation. You may also benefit from touching up on the essentials of server monitoring.

System Design Questions

8. What Is Active Directory?

Active Directory is a Microsoft product. It consists of several services that run on Windows Server to manage permissions and access to networked resources. Active Directory stores data as objects, which are single elements such as a user, group, application or device. Active Directory categorizes objects by name and attributes. For example, a user's name might include the name string, along with information associated with the user, such as passwords and Secure Shell (SSH) keys.

The main service in Active Directory is Domain Services (AD DS). AD DS stores directory information and handles the user's interaction with the domain. AD DS verifies access when a user signs into a device or attempts to connect to a server over a network. Administrators typically have different levels of access to data than end users. It is important to note that on-premises AD DS differs from Microsoft Azure Active Directory.

If asked about Active Directory, you should be comfortable explaining Group Policy. Group Policy is the hierarchical infrastructure that allows a network administrator in charge of Microsoft's Active Directory to implement specific configurations for users and computers. Explain how you've used Group Policy to define security settings.

AD Group Policy Management console
Admins can use Active Directory's Group Policy Management console to customize their organization's user and computer settings.

9. What IT Automation Tools Have You Used With Servers?

These software tools replace a series of actions and responses between an administrator and the IT environment. Here, your interviewer wants to know what experience you've had with Microsoft's PowerShell, CA Technologies' Server Automation, BMC Software's BladeLogic Server Automation, or other tools that automate system tasks, such as batch processing.

You're most likely to be asked about PowerShell. PowerShell has emerged as a critical tool for systems administrators, providing a consistent, adaptable technology for managing on-premises and cloud-based systems. Microsoft launched PowerShell in 2006 to work solely in the Windows environment, but the company open sourced the technology in 2016. Today, the tool aims to appeal to a wider range of admins, as it's now also available for Linux and macOS. PowerShell has also made the jump to broader computing models, spanning cloud environments such as Microsoft Azure and AWS.

If you are asked about PowerShell, be prepared to explain the benefits of Desired State Configuration (DSC) and its push and pull modes of operation.

10. What Is a Domain Controller?

OK, so this is as much a history question as it is a science question. Your interviewer may be fishing to see if you know that before Windows 2000, Microsoft's domain controllers were referred to as the primary domain controller (PDC) and backup domain controller (BDC) and were roles that could be assigned to a Windows NT network. They later became an integral part of Active Directory.

In any case, the role of a domain controller is to serve as a gatekeeper, responding to security authentication requests within a computer domain. At the simplest level, it provides or denies access -- for example, by a username and password -- to domain resources.

Networking Questions

11. How Many Layers Are in the OSI Model? Name and Explain Them.

Open Systems Interconnection (OSI) models how data is sent or received over a network. This model breaks down data transmission over a series of seven layers, each of which is responsible for performing specific tasks concerning sending and receiving data.

You may be asked to distinguish between OSI and TCP/IP. The main similarity is in their construction into layers. However, the OSI model consists of seven layers, while TCP/IP consists of just four layers.

The main concept of OSI is that the process of communication, between two endpoints in a network, can be divided into seven distinct groups of related functions, or layers. Each communicating user, or program, is on a device that can provide those seven layers of function.

OSI layers
A breakdown of OSI layers

The seven OSI layers are:

Layer 7: The application layer. The is the top of the OSI communications model. The application layer provides services for an application program to ensure that effective communication with another application program on a network is possible.

Layer 6: The presentation layer. This layer ensures that the communications that pass through it are in the appropriate form for the recipient application. 

Layer 5: The session layer. This layer manages the setup and teardown of the association between two communicating endpoints. 

Layer 4: The transport layer. This layer ensures the reliable arrival of messages across a network and provides error-checking mechanisms and data flow controls.

Layer 3: The network layer. The network layer's primary function is to move data into and through other networks.

Layer 2: The data-link layer. This serves as the protocol layer in a program that handles the moving of data into and out of a physical link in a network. 

Layer 1: The physical layer. This the lowest layer of the OSI communications model. The physical layer's function is to transport data using electrical, mechanical or procedural interfaces.

12. Explain the Difference Between a Client and a Server in Simple Terms.

Because client-server computing is nearly ubiquitous now, it should be a fairly straightforward explanation of how one program (the client) requests a service or resource from another program (the server). You might want to spend more time explaining the pros and cons of the client-server model, as well as the basics of client-server protocols, particularly TCP/IP.

You may want to explain that an important advantage of the client-server model is that its centralized architecture helps make it easier to protect data with access controls that security policies enforce. Also, you should note that it doesn't matter if the clients and the server are built on the same operating system because data is transferred through client-server protocols that are platform-agnostic. An important disadvantage, you can explain, is that if too many clients simultaneously request data from the server, it may get overloaded. In addition to causing network congestion, too many requests may result in a denial of service.

As for the client-server protocols, explain that clients typically communicate with servers by using the TCP/IP protocol suite. TCP is a connection-oriented protocol, which means a connection is established and maintained until the application programs at each end have finished exchanging messages. It determines how to break application data into packets that networks can deliver; sends packets to and accepts packets from the network layer; manages flow control; and handles retransmission of dropped or garbled packets, as well as acknowledgement of all packets that arrive. In contrast, IP is a connectionless protocol, which means that there is no continuing connection between the endpoints that are communicating. Each packet that travels through the internet is treated as an independent unit of data, without any relation to any other unit of data.

13. How Do DNS Servers Function?

There are three types of domain name system servers: DNS stub resolver servers, DNS recursive resolver servers and DNS authoritative servers. DNS servers answer questions from both inside and outside their own domains. When a server receives a request from outside the domain for information about a name or address inside the domain, it provides the authoritative answer. When a server receives a request from inside its own domain for information about a name or address outside that domain, it passes the request out to another server. Usually, this server is one managed by its internet service provider (ISP).

If that server does not know the answer or the authoritative source for the answer, it reaches out to the DNS servers for the top-level domain (e.g., for all of .com or .edu). Then, it passes the request down to the authoritative server for the specific domain (e.g., techtarget.com or stkate.edu). The answer flows back along the same path.

14. Differentiate Between Attenuation, Distortion and Noise

Attenuation in computer networking is the loss of communication signal strength, measured in decibels (dB). As the rate of attenuation increases, the transmission, such as an email a user is trying to send or a phone call, becomes more distorted. Attenuation can occur on computer networks due to range, interference (e.g., by radio interference or physical obstructions), or wire size (the thinner the wire, the greater attenuation).

Distortion refers to the change in shape of a signal. Distortion happens most often when signals are composites of different signals on different frequencies travelling across different mediums.

Noise is probably the most recognizable of the three. It describes a jumble of mixed signals, thermal noise and other noises.

15. What Are the Benefits of Using Subnets?

There are three key benefits to using subnets, which represent the logical partition of an IP network into multiple, smaller network segments: 

  • Reallocating IP addresses. Each class has a limited number of host allocations; for example, networks with more than 254 devices need a Class B allocation. If a network administrator is working with a Class B or C network and needs to allocate 150 hosts for three physical networks located in three different cities, they would need to either request more address blocks for each network or divide a network into subnets that enable administrators to use one block of addresses on multiple physical networks.
  • Relieving network congestion. If much of an organization's traffic is meant to be shared regularly among the same cluster of computers, placing them on the same subnet can reduce network traffic and improve performance. Without a subnet, all computers and servers on the network would see data packets from every other computer.
  • Improving network security. Subnetting allows network administrators to reduce network-wide threats by quarantining compromised sections of the network and by making it more difficult for trespassers to move around an organization's network.

As with any job interview, it's important for the candidate to anticipate questions from the interviewer and come prepared. To prepare, it can be helpful to practice answering these questions by participating in mock interviews. Practicing with a partner who has experience with servers, systems design and networking can be advantageous, as they can provide constructive feedback for your answers.

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