1

參考答案

At my previous job, I was tasked with implementing a new Voice over IP (VoIP) phone system for our organization, as our old system had reached the end of its life and was no longer meeting our needs. The company had around 200 employees, so it was crucial to ensure a smooth transition with minimal disruption. First, I researched and evaluated several VoIP vendors before choosing one that offered the best value and features for our organization. I then developed a project plan that included timelines, key milestones, and potential risks. I worked closely with the vendor to ensure that all hardware and software components were delivered on time and were compatible with our existing network infrastructure. Next, I organized training sessions for our IT support team, so they were well-equipped to handle any issues that might come up during the installation and transition. I also set up communication channels for employees to provide feedback and report any issues they encountered during the transition. During the implementation phase, I worked closely with our IT support team to address any issues that arose and ensured that the new system was fully operational before decommissioning the old system. We faced a few challenges along the way, such as coordinating with remote employees and ensuring proper training for all users, but we were able to overcome these obstacles through clear communication and by prioritizing tasks effectively. In the end, the new VoIP system led to improved audio quality, better integration with other applications, and significant cost savings for the organization. It was a challenging yet rewarding experience, and I'm proud of how my team and I successfully implemented the new technology with minimal disruption to employees.

2

參考答案

By asking about the candidate's approach to leading a team through such a project and requesting an example of a successful project they've managed, you can gain insights into their strategic planning, communication skills, and ability to execute complex initiatives.

3

參考答案

The Transmission Control Protocol (TCP) is a connection-based protocol that uses acknowledgment and retransmission for lost packets to ensure dependable data transfer. On the other hand, the UDP (User Datagram Protocol) is connectionless and does not guarantee delivery, making it faster but less reliable. It is often used in applications where speed is critical, and minor data loss is acceptable, such as streaming or gaming.

4

參考答案

A hub serves as a fundamental device in networking, linking several computers or network devices without regulating the traffic it handles. It broadcasts incoming data packets to all its ports indiscriminately. In contrast, a switch connects network devices and intelligently directs data to the correct recipient based on MAC addresses, reducing unnecessary traffic and enhancing the network's overall efficiency. A router connects distinct networks, guiding data packets among them by utilizing IP addresses. Unlike switches and hubs, routers are capable of executing Network Address Translation (NAT) and are equipped with more sophisticated security functionalities.

5

參考答案

I have experience with cloud networking and hybrid environments, including configuring and managing network resources on platforms like AWS, Azure, and Google Cloud. This includes setting up VPNs, virtual networks, and security groups to ensure seamless connectivity between on-premises and cloud environments. Hybrid environments require careful integration and management to ensure performance, security, and reliability.

6

參考答案

Memorize the common ones and know where would you use them (VLAN vs P2P vs Core) Know the Classes of Addresses and ranges including the experimental and reserved. Also know why we use them, how a computer reads the Network/Host bits and why there's a mathematical limit and how this was increased in IPv6.

7

參考答案

A DNS resolver is a component of the Domain Name System (DNS) that is responsible for translating domain names (e.g., www.example.com) into their corresponding IP addresses (e.g., 192.0.2.1) so that devices can locate and connect to websites or other services on the Internet. How DNS Resolver Works: - DNS Query: When a user enters a website address in their browser, the DNS resolver receives the domain name query. - Recursive Search: The resolver starts the process by querying a series of DNS servers, including root DNS servers, authoritative DNS servers, and caching DNS servers, to find the IP address associated with the domain. - Return IP Address: Once the DNS resolver finds the correct IP address, it returns this information to the requesting device (e.g., your computer), which can then use it to establish a connection. Types of DNS Resolvers: - Recursive Resolver: Performs the entire DNS lookup process for the client. - Caching Resolver: Stores DNS query results for a set time to speed up future lookups. DNS resolvers are essential for translating human-readable URLs into machine-readable IP addresses.

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參考答案

The best part of this question is that you'll be able to identify the candidate's level of experience. The size of the network outage caused by the candidate can reveal the scale of environments they've worked in and the level of responsibility they've had in their previous roles. A candidate who has managed to resolve a significant outage on a large network demonstrates their ability to handle high-pressure situations and effectively coordinate with cross-functional teams to restore services promptly.

9

參考答案

A VPN stands for Virtual Private Network, a technology that allows a secure tunnel to be created across a network like the Internet. For example, VPNs enable you to set up a secure dial-up connection to a remote server, masking your IP geolocation to protect your identity and maintain privacy online.

10

參考答案

• An SSL certificate authenticates a website's identity and encrypts data exchanged between the user and the site.

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An IP address (Internet Protocol address) is a unique numerical label assigned to each device connected to a network, enabling devices to identify and communicate with one another. It functions similarly to a home address in the physical world: just as a house needs an address for people to find it, devices require an IP address to send and receive data. There are two types of IP addresses: - IPv4 (Internet Protocol Version 4): This is the older and most widely used version, using a 32-bit address format, which allows for approximately 4.3 billion unique addresses (e.g., 192.168.1.1). - IPv6 (Internet Protocol Version 6): Due to the limited number of available IPv4 addresses, IPv6 was introduced with a 128-bit address format, providing an almost infinite number of addresses (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). An IP address enables devices to be identified, and it is used to route data from one device to another across the network. There are two main categories of IP addresses: - Static IP Address: Manually configured and remains the same over time. - Dynamic IP Address: Automatically assigned by a DHCP (Dynamic Host Configuration Protocol) server and can change over time.

12

參考答案

Some services provided by the application layer in the Internet model are as follows: - Mail services - Directory services - File transfer - Access management - Network virtual terminal

13

參考答案

A Layer 2 switch operates at the data link layer of the OSI model, where it uses MAC addresses to forward data frames. It learns and maintains a MAC address table by inspecting incoming frames, associating each MAC address with a specific port. When a frame arrives, the switch checks the destination MAC address and forwards it to the corresponding port, ensuring efficient and accurate delivery within a local network.

14

參考答案

1. Use efficient routing protocols. 2. Increase bandwidth. 3. Implement QoS. 4. Upgrade hardware to support higher speeds.

15

參考答案

Some of my biggest successes in network engineering include designing and implementing highly available and scalable network architectures, as well as troubleshooting and resolving complex network issues. I have also been successful in developing and managing teams of network engineers, and have played a key role in mentoring and training junior staff.

16

參考答案

The introduction of IPv6, despite the widespread use of Network Address Translation (NAT) with IPv4, addresses several key limitations and offers significant advantages that NAT cannot fully resolve. NAT was developed as a temporary solution to the exhaustion of IPv4 addresses, allowing multiple devices on a private network to share a single public IPv4 address. While NAT effectively extends the life of the IPv4 address space and provides a layer of privacy and security by hiding internal IP addresses, it introduces complexity and limitations in network configuration and communication. IPv6, on the other hand, offers a vastly expanded address space due to its 128-bit address size, compared to the 32-bit size of IPv4. This expansion virtually eliminates the need for NAT, allowing every device to have a unique global address.

17

參考答案

Dynamic Host Configuration Protocol (DHCP) automatically assigns IP addresses, subnet masks, default gateways and other network parameters to network clients. Lease behavior defines the time period a client can use the assigned IP address: the client will send renewal requests at 50% of the lease time, and if renewal fails, it will try again at 87.5% of the lease time, and release the IP once the full lease expires.

18

參考答案

A VLAN lets you segment a physical network into multiple logical networks. Devices on the same VLAN can communicate as if they were on the same switch, even if they are spread across a building. Security is the big reason to use them. You can isolate sensitive systems from general user traffic. If someone plugs a compromised laptop into the network, the damage stays contained to their VLAN. VLANs also improve performance by reducing broadcast domain size. In my previous role, we had separate VLANs per department, which made it easier to apply different QoS policies for teams that relied heavily on phone calls.

19

參考答案

The internet is a vast global network of interconnected computer networks that use the TCP/IP protocol suite to communicate. It's the physical infrastructure – the cables, routers, and servers – that allows data to travel. Think of it as the roads and highways. The World Wide Web (WWW), on the other hand, is a collection of interconnected documents (web pages) and other resources, linked by hyperlinks and URLs. It's accessed over the internet using protocols like HTTP. Think of the WWW as the traffic – the cars, trucks, and buses – that travel on those roads. In short, the internet is the underlying network, while the World Wide Web is one of the services that runs on top of it. Email, file transfer (FTP), and online gaming are other examples of services that also use the internet.

20

參考答案

You are expected to explain what Git version control system is, list the key benefits you can get when you use Git to manage your network configuration, script and infrastructure as code files.

21

參考答案

I once worked on a project to upgrade a network infrastructure for a high-profile customer. The challenge was coordinating with multiple teams to minimize downtime. I created a detailed project plan, held regular status meetings, and communicated effectively with all stakeholders. This proactive approach helped us have a smooth transition with minimal disruption.

22

參考答案

NetFlow is a protocol for collecting IP traffic information. It provides visibility into traffic patterns and usage, helps identify traffic sources and destinations, and enables monitoring of bandwidth usage, detection of anomalies, and enhancement of network security.

23

參考答案

This question is a protocol-based technical question for network engineer interviews. To answer it properly, you need to master the core knowledge of all layers and corresponding protocols under the OSI and TCP/IP Models, to demonstrate your solid networking fundamental understanding.

24

參考答案

MPLS (Multiprotocol Label Switching) routes data efficiently by using labels instead of IP addresses.

25

參考答案

A subnet mask is used to divide an IP address into a network and host portion, defining which part of the address refers to the network.

26

參考答案

DNS (Domain Name System) is the internet's mechanism for converting human-readable website names (such as www.example.com) into IP addresses (such as 192.0.2.1), that computers use to recognize one another within the network. Whenever you type a website address into your browser, your computer consults DNS to retrieve the corresponding IP address from a DNS server. With this IP address, your computer is able to establish a connection to the server hosting the website.

27

參考答案

Yes, you can connect two computers back to back using a crossover cable for file sharing. Cross over cable's one end of data transmit pin is connected to the other end data receive pin and vice versa.

28

參考答案

Quality of Service (QoS) refers to the set of technologies and techniques that manage network resources by prioritizing certain types of data traffic. This is crucial, especially in environments where critical applications, such as VoIP or video conferencing, require guaranteed bandwidth and low latency. By implementing QoS policies, I can ensure time-sensitive data is transmitted efficiently without being delayed by less critical traffic. For example, prioritizing voice data packets over standard web browsing traffic during peak usage times can maintain call clarity and reliability.

29

參考答案

• 2.4 GHz provides broader coverage but slower speeds. • 5 GHz offers faster speeds but shorter range.

30

參考答案

The OSI model has seven layers, and I think of it as a troubleshooting framework. When we have a connectivity issue, I start at the bottom. If users can't reach a resource, I first confirm that physical cables are plugged in and the interface is up—that's Layer 1. Then I check Layer 2 for VLAN assignments and switch configurations. If the device is on the right VLAN but still can't communicate, I move to Layer 3 and check IP addressing, subnet masks, and routing. I once had a situation where users in one department couldn't reach a server in another building. By systematically working through the layers, I found the issue was at Layer 3—the router wasn't advertising the correct route. Knowing the model helps me avoid wasting time on irrelevant checks.

31

參考答案

You can make comparison between access control list (ACL) based stateless firewall and stateful firewall that tracks full connection status, explain their difference on logic and performance.

32

參考答案

Legacy systems often lack compatibility with modern protocols, leading to integration challenges and security risks. I address these issues by using gateways, protocol converters, and thorough testing to ensure interoperability. This careful approach minimizes disruptions while modernizing the network infrastructure.

33

參考答案

Network segmentation divides a network into smaller segments to limit access and contain potential threats.

34

參考答案

The obvious answer to this question is yes or no, but you should elaborate if the answer is yes. Most networking environments use a combination of Windows and Linux servers and desktops. Usually, network engineers prefer Linux servers and work with Windows and Linux desktops. Occasionally, you might have some Mac desktops as well to work with.

35

參考答案

• IPv4 uses 32 bits and allows approximately 4.3 billion unique addresses. • IPv6 uses 128 bits, allowing for a virtually infinite number of unique addresses.

36

參考答案

Gateways typically operate at the network layer, though they can function across multiple layers depending on their configuration. They connect networks using different protocols, facilitating seamless communication between them. This versatility makes gateways a crucial component in heterogeneous network environments.

37

參考答案

The Domain Name System (DNS) translates human-readable domain names (like www.example.com) into IP addresses that computers use to identify each other on the network. When a user enters a domain, the DNS server checks if it has a cached IP address. If not, it queries other DNS servers to resolve the IP, enabling the browser to load the correct website. DNS is essential for simplifying access to online resources without needing to remember complex IP addresses.

38

參考答案

I use Wireshark for packet analysis and SNMP for monitoring device performance. They help in diagnosing issues and optimizing networks.

39

參考答案

I ensure the scalability of a network infrastructure by designing it with modularity and flexibility in mind. This includes implementing scalable hardware, using hierarchical network designs, and leveraging technologies like VLANs and virtual networks. Regular capacity planning, monitoring, and performance analysis help identify potential bottlenecks and ensure the network can grow with the organization's needs.

40

參考答案

1. Choose a VPN type (site-to-site or remote access). 2. Set up VPN servers or routers. 3. Configure encryption protocols like IPsec. 4. Test and monitor the connection.

41

參考答案

I take a few different approaches. I maintain my Cisco certifications and am currently working toward my CCNP. The study process forces me to go deep on topics I might not encounter daily. I also follow Network World and Cisco's blog, and I am part of a local network engineering meetup where we share solutions. Most valuable is hands-on experimentation. I have a home lab where I test configurations without risking production systems. Lately I have been exploring software-defined networking and learning Python for network automation. That is where the field is heading.

42

參考答案

A network is a collection of devices that communicate to share resources and information. There are different network types such as PAN, LAN, MAN, and WAN that can be introduced with appropriate context. Networks enable connectivity between nodes and devices within various geographic scopes.

43

參考答案

A proxy server is a program that acts as an intermediary between a client and a server. The primary function of a proxy server is to allow clients to request data from one or more servers on the Internet without disclosing the client's internal private IP address. This is often done for security reasons, to mask the location of a network from unauthorized individuals, or simply to hide its existence from other computers on the Internet.

44

參考答案

WAN is a Wide Area Network. It connects computers across different places or countries.

45

參考答案

Edge computing processes data closer to the source to reduce latency and improve efficiency.

46

參考答案

An interviewer may ask you this question to evaluate how interested you are in progressing in network engineering. Example response: "I recognise that staying up-to-date with the latest network engineering trends, products, and technologies is essential to my career, especially given the rapid pace of the IT industry. To achieve this, I actively engage in various online professional groups where we exchange ideas and explore new concepts. I also stay informed by subscribing to multiple podcasts and attending an annual IT conference. Additionally, I try to enrol on the latest courses and certifications and complete them in my own time to keep my knowledge of network engineering up-to-date."

47

參考答案

DNS, or Domain Name System, translates human-friendly domain names into IP addresses. This conversion is essential for routing internet traffic efficiently. I've configured and troubleshooted DNS systems to ensure smooth resolution and connectivity for end users.

48

參考答案

This is an FTP server that does not ask for a username or password for authentication. Instead, most of the time, you get an anonymous ftp server for specific public servers directories. And these directories are public directories or directories where information is released to the public.

49

參考答案

Bandwidth is a measurement that indicates the highest possible data transmission capacity of a wireless or wired communication channel within a network connection during a specific time frame. Higher bandwidth means more data can be sent and received faster and with fewer errors.

50

參考答案

You are expected to list all the IKE negotiation phases of Site to Site IPsec VPN, and list all the required pre-configured parameters on both tunnel peers to successfully bring up the VPN tunnel.

51

參考答案

Effective network capacity planning involves analyzing current usage trends and predicting future growth. I utilize tools for bandwidth monitoring and conduct regular assessments of network traffic patterns. This data helps me identify bottlenecks and plan for upgrades, ensuring the network can accommodate growth without degradation in performance.

52

參考答案

When troubleshooting a network issue, I typically follow these steps: - First, I will check the physical connections, ensuring cables and devices are properly connected. - Next, I will verify the device's IP address configuration to ensure it's correctly set up. - I then use tools like ping or tracert to test connectivity and trace the route of data packets. - Additionally, I would check network logs and configuration files for errors or misconfigurations. - Finally, I will test various network components to pinpoint the source of the problem, whether it's a router, switch, or cabling issue.

53

參考答案

Stay updated with relevant industry standards and regulations. Implement regular compliance audits and assessments. Document and enforce compliance policies and procedures. Example Answer: I stay updated with industry standards and regulations by regularly attending training sessions and reviewing compliance documentation. I also conduct periodic audits to ensure our network designs meet all necessary requirements, proactively addressing any potential issues.

54

參考答案

You are expected to explain the core working logic, features, pros and cons difference between Link State routing protocol and Distance Vector routing protocol.

55

參考答案

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to devices on a network.

56

參考答案

A router is a hardware component responsible for facilitating communication between various networks and devices. The key functions of a router encompass managing interactions between distinct networks, determining the optimal paths for device communication, as well as forwarding and filtering packets to ensure efficient data transmission.

57

參考答案

Latency is the time it takes for data to make a round trip. We measure latency in milliseconds. A low number is good. A high number is bad. You send a message and wait for a response. The time you wait is referred to as latency. It is the time for a signal to travel to a server and then come back to you. When playing an online game, low latency is crucial. High latency causes lag. It makes the game feel slow. The same applies to video calls. High latency makes conversations difficult. It is not the same as speed. Speed, or bandwidth, is how much data you can move at once. Latency refers to the time it takes for any piece of data to travel. You can have a fast connection with bad latency. This would feel like a big highway with a long delay at a traffic light.

58

參考答案

Some of the reasons for this issue can be: - Next-hop IP might be wrong - The return route might be wrong - Interface down - The subnet mask might be wrong - Routing loops - The firewall may be blocking the traffic You can verify using these commands: "show ip route ping traceroute" You should also make sure that the destination device has a route back to the source network.

59

參考答案

My approach to disaster recovery planning involves developing a comprehensive strategy. It includes regular data backups, creating failover systems, and establishing clear recovery point and recovery time objectives (RPO and RTO). I also conduct drills to ensure the team is prepared to execute the plan efficiently in the event of a disaster.

60

參考答案

A router links various networks and finds the optimal route for sending data packets from the source to the destination, using routing protocols like OSPF, BGP, or EIGRP. Routers operate at Layer 3 of the OSI model (network layer) and can also perform Network Address Translation (NAT) and packet filtering for security.

61

參考答案

IPSec has two modes of operation: Tunnel and Transport. IPSEC Tunnel Mode transmits data over the Internet that encrypts both the data and the original IP address. The ESP operates in Transport or Tunnel Mode. In Tunnel Mode, ESP encrypts both data and IP headers.

62

參考答案

Subnetting is a crucial concept in networking, and I've found that it serves two primary purposes: improving network performance and enhancing security. By dividing a larger network into smaller subnets, we can reduce congestion, minimize broadcast traffic, and better manage IP address allocation. The process of subnetting involves taking an IP address range and dividing it into smaller, more manageable segments by modifying the subnet mask. In my experience, a useful analogy I like to remember is that subnetting is like organizing a large group of people into smaller teams, making it easier to manage and communicate. For example, let's say I'm working on a project where I need to create a network for a company with four departments, each requiring 30 hosts. To optimize network performance and security, I'd subnet the IP address range 192.168.1.0/24. By modifying the subnet mask to /27 (255.255.255.224), I can create eight smaller subnets, each supporting up to 30 hosts. This helps me meet the specific requirements of the project while optimizing network performance and security.

63

參考答案

A VPC is a logically isolated section of a public cloud where you can launch resources in a virtual network you define. It's important because it provides network isolation, security, and control over network configuration. This allows organizations to create a private and secure environment. They can achieve this within a public cloud infrastructure.

64

參考答案

Network segmentation divides a network into smaller, isolated subnetworks, often using VLANs. This offers several key benefits. It significantly improves security by limiting the "blast radius" of security breaches. If one segment is compromised, the impact is contained, preventing the entire network from being affected. Segmentation can also enhance performance by reducing broadcast traffic within each segment. This reduces congestion and improves overall network efficiency. It also simplifies network management by allowing administrators to manage smaller, more manageable units.

65

參考答案

Hardware components tend to fail over time, and there are many ways that this can happen. For example, a device can age and stop working. Even a hard drive or storage device can malfunction, NIC (Network Interface Card) can be broken, and a computer or network device can overheat and burn chips inside. Sometimes hardware misconfiguration can also cause trouble; for example, you forgot to enable a second power supply or accidentally switched off the Core device.

66

參考答案

Spanning Tree Protocol (STP) dynamically disables redundant layer 2 links in a switched network to build a loop-free logical tree topology by selecting a root bridge, assigning root ports to non-root bridges, and blocking designated ports on redundant paths, while still activating blocked links to provide redundancy if an active path fails.

67

參考答案

VRF (Virtual Routing and Forwarding) is a technology used to create multiple independent routing tables within a single router, effectively allowing one router to act as multiple routers. Each VRF instance is isolated and has its own set of routes, interfaces, and forwarding decisions. How VRF Works: - Multiple Virtual Routers: VRF allows a router to maintain multiple routing tables, each associated with a different virtual network. These routing tables are independent, meaning that the same IP address can be used in different VRFs without conflict. - Traffic Isolation: Since VRFs are isolated from one another, traffic in one VRF cannot interact with or be routed into another VRF unless explicitly configured (e.g., using inter-VRF routing or route leaking). - Efficiency: VRF enables the consolidation of multiple networks onto a single physical device without compromising security or network segmentation. Use Cases: - Service Providers: VRF is commonly used by ISPs to provide multiple virtual networks for different customers over a shared infrastructure. - Enterprise Networks: It is also used within large enterprises to segment networks (e.g., separating voice, data, and guest networks).

68

參考答案

VPN stands for Virtual private network. - It is considered VIRTUAL because it establishes a digital pathway, without needing a physical cable, between the user's device and the VPN server. - It is considered PRIVATE due to its ability to encrypt user data and conceal their Internet Protocol (IP) address. - It is considered a NETWORK due to its ability to connect various computing devices, namely the user's device and the VPN server. Virtual Private Networks simplify the transmission of all network traffic to a virtual network, thus allowing users to access local network resources remotely and bypass Internet censorship. The majority of operating systems have built-in VPN support. VPNs were initially designed to connect separate corporate networks over the internet securely or to provide remote access to a company's network.

69

參考答案

Interviewers ask this question as they'll want to know if you have experience designing, implementing and troubleshooting networks similar to or the same size as the networks they and their clients use. Example response: "Among the networks I've designed, implemented, and provided troubleshooting support on, the biggest one I worked on was with my former employer. This project involved interconnecting numerous locations across the country, providing seamless communication for their employees working both onsite and remotely around the world - the latter of which involved me setting up secure VPNs to enable safe access to the network from remote locations."

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參考答案

You can use any tools to troubleshoot issues, but you should mention some internal typical commands that help troubleshoot standard problems. For instance, if the user can't access the Internet, you might want to run a tracert on the problem. You could also use ping to see if the user can access internal areas of the network. Of course, there could also be hardware issues such as a bad network card or broken cable.

71

參考答案

An experienced engineer deploys OSPF for intra-domain routing with hierarchical areas and fine-tunes LSAs, cost metrics, and DR/BDR roles. For BGP, they manage routing between autonomous systems, implement route filters and attributes for policy control, monitor route convergence, and troubleshoot using protocol-specific debugs and visualizations.

72

參考答案

The three-way TCP handshake is the process by which two devices establish a reliable connection before data can be transmitted over a TCP/IP network. It ensures that both devices are synchronized and ready to communicate. Steps of the Three-Way Handshake: - SYN (Synchronize): - The client sends a TCP packet with the SYN flag set to the server. This packet indicates that the client wants to initiate a connection and synchronize sequence numbers. - The packet includes a sequence number that is randomly generated. - SYN-ACK (Synchronize-Acknowledge): - The server responds with a packet that has both the SYN and ACK flags set. - The ACK acknowledges the client's SYN request by setting the acknowledgment number to one more than the sequence number received from the client. - The server also includes its own sequence number in the SYN part of the message. - ACK (Acknowledge): - The client sends an ACK packet back to the server to acknowledge the receipt of the server's SYN-ACK packet. - This completes the handshake, and the connection is established. After the handshake, data can begin to be transmitted in both directions, and the TCP connection is considered established.

73

參考答案

Anonymous FTP allows users to access files on a server without requiring a personalized login. It's often used for distributing public data, though security considerations are paramount. In my role, I've configured anonymous FTP for controlled environments while ensuring proper access restrictions.

74

參考答案

A three-way handshake is used in TCP/IP to establish a reliable connection between a client and a server. It begins with the client sending a SYN packet to the server, signaling a request to establish a connection. The server responds with a SYN-ACK packet, acknowledging the request. Finally, the client acknowledges the server's response with an ACK packet. After this, the connection is established.

75

參考答案

VPN stands for Virtual Private Network, and it is a way of using a public network to connect to a private network. A VPN allows you to create a secure tunnel between two locations over the WAN or Internet. You can use a VPN to encrypt all the data you send across the Internet. This prevents your ISP from reading it, and it also prevents anyone trying to snoop on your traffic from reading it.

76

參考答案

Network Address Translation (NAT) enables private IP networks that use unregistered IP addresses to connect to the public internet. NAT operates on a router, usually connecting two networks together, and translates the private (not globally unique) addresses in the internal network into a legal public IP address before packets are forwarded on the internet. It helps conserve the global IP address space.

77

參考答案

Choose a relevant example with significant impact. Explain your approach to simplifying technical jargon. Highlight the positive outcome and feedback received. Example Answer: During a company-wide meeting, I explained the importance of network security to non-technical staff by using simple analogies, like comparing firewalls to locked doors. This approach helped everyone understand the critical role they play in maintaining our network's safety.

78

參考答案

Maintenance windows, rollback plans, configuration backups, stakeholder communication, and testing in lab environments when possible.

79

參考答案

Quality of Service (QoS) is a networking feature that gives important network traffic higher priority than less important traffic. In simple words, it controls which data should move first in the network when the network gets busy. A network carries many types of data: - Video calls - Voice calls - YouTube Videos - File Downloads - Emails - Online games, etc. But not all traffic is equally important. Without QoS, all the traffic is treated the same way, which can cause: - Voice breaking - Video buffering - Slow application performance - Lag during meetings, etc. QoS solves these problems by giving priority to important traffic.

80

參考答案

The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on IP networks. DHCP automates the process of assigning reusable network configurations to devices on a network—this includes IP addresses, the subnet mask, default gateway, and DNS server information. Without DHCP, network Administrators would need to manually configure each device in the network.

81

參考答案

NAT (Network Address Translation) is a technique used to modify IP addresses in packets as they pass through a router or firewall. It allows multiple devices on a private network to share a single public IP address for accessing external networks. NAT helps conserve public IP addresses and enhances security by hiding internal IP addresses from external networks.

82

參考答案

Routers are layer3 devices, and their main task is to provide routing between two networks or two network segments. However, they are smart enough to provide other network services, including DHCP, DNS, default gateway, logging, firewall, etc. In addition, most of the home modems have inbuilt routers and firewalls, and you can use them to restrict/allow computers for certain websites at a particular time of day, event and data logging, and much more.

83

參考答案

We can get an IP address from a domain name using ping commands and nslookup command. For this, use command-line tools like PING or nslookup to get the IP address. Run the commands “PING example.com” or “nslookup example.com” on command prompt or terminal window.

84

參考答案

The main goal of a DoS, or Denial-of-Service attack, is to disrupt the network services provided to a large group of people at the same time. The impact of a DoS attack is often measured by the number of users who cannot use the service and the time required to restore it. A DoS attack usually takes place with the help of bots that a hacker or a malicious individual controls. The goal of a DoS attack is to cause a service to crash or to make it unavailable. It is usually done by flooding the service with too many requests for information or requests for service. These requests use up the server or network resources and can make it difficult or unable to provide the service.

85

參考答案

The common types of networks include: - WANs (wide area networks) - LANs (local area networks) - MANs (metropolitan area networks) - PAN (personal area network) - GANs (global area networks) - WLAN (wireless local area network) - SAN (storage area network) - DAN (desk area network) - CAN (campus area network) - VoIP (voice over internet protocol) Example description of WAN: "WAN, which stands for Wide Area Network, refers to the interlinking of computers and devices across vast geographical distances. It facilitates the connection of networks spread across different regions and countries, enabling seamless communication, and data exchange."

86

參考答案

A VPN (Virtual Private Network) creates a secure, encrypted connection over a public network.

87

參考答案

Port forwarding allows remote devices to connect to a specific device or service within a private network by redirecting network traffic through specific ports.

88

參考答案

Encryption is scrambling a data string into a format that a receiver can only interpret with access to the encryption key. Encryption ensures that information captured halfway remains unreadable. Without encryption, anyone on the network could read everything.

89

參考答案

SDN (Software-Defined Networking) separates the control plane from the data plane, enabling centralized network management.

90

參考答案

Restrict Inbound traffic to DMZ zone, Allow necessary internal access to DMZ, implement proper ACL and firewall rules to separate DMZ, internal trusted network and external public network.

91

參考答案

Address sharing is done through NAT (Network Address Translation), and it allows multiple inside hosts to share the same Public IP address. You need a special device capable of doing NAT, for example, a router or a firewall. Address translation not only saves Public IP addresses but also has an inherent security benefit compared to routing. That's because servers on the Internet can only see the public IP address of the external interface of the firewall, not the host's private IP address behind it. The firewall has an inbuilt NAT table for address translation which maps public ip addresses and ports with Private IP addresses and ports of every connection.

92

參考答案

A forward proxy and a reverse proxy both work as a middleman in a network, but their differences lie in who they protect and where they are placed in a network.

93

參考答案

A hub broadcasts data to every port on the network and is the least complicated of these devices. Switches are similar to hubs but are more efficient by dynamically creating connections and providing data only to the port requested. Routers come in all shapes and sizes and are the most complicated of these three devices. Their purpose is to route network traffic.

94

參考答案

Here are some benefits of SD-WAN: - It simplifies WAN Management. - It reduces WAN costs. - Provides more security. - Increased Bandwidth and efficiency. - It provides easier network management.

95

參考答案

Peer-to-peer (P2P) networks are networks that do not rely on a central server for their operation. All of the computers connected to this network function as individual workstations.

96

參考答案

I stay current with networking technologies by attending industry conferences, participating in webinars, and following reputable tech blogs and forums. I also pursue continuous education through certifications and online courses, which keep my skills sharp and ensure I am aware of emerging trends and best practices in the networking field.

97

參考答案

Network defects can often arise from software issues such as incorrect configurations, where settings are not properly aligned with the network's operational requirements. Another common problem is outdated software that lacks the latest security patches or performance improvements, leading to vulnerabilities or inefficiencies. Bugs in the network software can also cause unexpected behaviors, disrupting the flow of data. It's like having outdated or incorrect maps in our highway analogy; drivers (data packets) might end up in the wrong place or face unnecessary delays.

98

參考答案

You are expected to explain the seamless roaming process that a WiFi client device keeps its network connection active when it moves out of the coverage of current associated AP and connects to another nearby AP of the same WLAN SSID.

99

參考答案

I like your company's focus on innovation and technology. Your projects in networking technology resonate with my career goals, and I'm looking forward to being part of a team that values continuous learning and professional growth.

100

參考答案

MPLS (Multiprotocol Label Switching) and Segment Routing are traffic engineering technologies that allow network operators to define custom end-to-end traffic paths independent of the default shortest path routing, to steer specific high priority traffic along pre-defined low-congestion paths, balance network load evenly across all links, and make efficient use of available network bandwidth to avoid bottlenecks.

101

參考答案

The main difference between a static IP address and a dynamic IP address lies in how the IP addresses are assigned to devices: - Static IP Address: - A static IP address is a fixed, manually assigned address that does not change over time. - It is typically assigned to servers, network devices, and other critical systems that require consistent addressing (such as web servers, email servers, or printers). - Advantages: Static IPs are necessary for services that require a constant address, such as hosting a website or a VPN server. - Disadvantages: Static IPs are often more vulnerable to attacks (since they are predictable) and can be more costly because they consume a permanent address from the available pool. - Dynamic IP Address: - A dynamic IP address is automatically assigned by a DHCP (Dynamic Host Configuration Protocol) server when a device joins the network. - The IP address can change each time the device connects to the network or after a certain lease time expires. - Advantages: Dynamic IPs are cost-effective and efficient because they allow the reuse of IP addresses among multiple devices. - Disadvantages: Since dynamic IPs change frequently, they are less suitable for services requiring a fixed IP (like hosting a website).

102

參考答案

SSID (Service Set Identifier) is the name assigned to a wireless network, which devices use to connect.

103

參考答案

Designing a scalable network requires planning for future growth and flexibility. The core process includes: - Implement a modular architecture, using hierarchical models like core, distribution, and access layers - Use scalable technologies like VLANs and IP subnets to segment traffic - Implement redundant links and devices to handle increased traffic loads - Choose equipment that supports higher capacity and can be upgraded easily - Plan for efficient routing and switching to minimize bottlenecks, and ensure the network can accommodate new users, devices, and applications

104

參考答案

EIGRP (Enhanced Interior Gateway Routing Protocol) is a hybrid routing protocol combining features of distance-vector and link-state protocols. It uses the Diffusing Update Algorithm (DUAL) for rapid convergence and minimizes network disruptions. Unlike RIP, which has a hop limit and slower convergence, EIGRP supports classless routing, VLSM, and complex metrics. Compared to OSPF, EIGRP is easier to configure and scales well in diverse networks, though it is proprietary to Cisco devices, limiting its interoperability with non-Cisco equipment.

105

參考答案

Our main data center lost connectivity to branch offices during peak hours. Sales teams across three states could not access the CRM, and our primary network engineer was on vacation. I started with our monitoring tools. Alerts pointed to the core router, but it looked healthy. When I checked our BGP sessions with the ISP, I found one had dropped. The logs showed an automated security update had modified some prefix filters, causing our routes to stop being advertised. I rolled back the configuration, verified the BGP sessions came back up, and restored connectivity in about 45 minutes. Afterward, I documented everything and helped implement a change approval process to catch these conflicts before they hit production.

106

參考答案

Penetration testing simulates attacks on a network to identify vulnerabilities and improve security.

107

參考答案

You need to have solid technical skills backed with hands-on experience, good problem-solving ability, excellent written & verbal communication skills, passion for the field, and do exhaustive preparation before the interview.

108

參考答案

I've found that the Border Gateway Protocol, or BGP, is a crucial component for ensuring the smooth operation of the internet. It's interesting because BGP is a path vector protocol that functions by exchanging routing information between routers. In my experience, BGP is essential for connecting autonomous systems (AS), which are individual networks managed by different organizations. BGP is critical for internet routing because it allows routers to select the best path for forwarding traffic based on various attributes, such as the number of AS hops or the shortest path. This helps me ensure that traffic flows efficiently across the internet, and it allows for load balancing and network resilience in case of link failures or congestion.

109

參考答案

Blockchain ensures secure, transparent, and tamper-proof transactions and communications in decentralized networks.

110

參考答案

I segment networks into VLANs based on departments or functions, improving traffic isolation and manageability.

111

參考答案

The modern modem is a device that offers a digital connection for voice, video, and data. The modem is an abbreviation of MOdulator DEModulator. The purpose of a modem is to modulate a digital signal to an analog signal and demodulate an analog signal to a digital signal. Telecom companies use practically many modems, which are the specialized hardware that they use for exchanging data over a telephone line, satellite link, or a cable network with another computer.

112

參考答案

You are expected to explain the definition of Virtual Private Cloud, then list two proper layer 3 network isolation mechanisms to secure the VPC environment.

113

參考答案

Virtual LANs, or VLANs, are virtual separations within a switch that provide distinct logical LANs, and each behaves as if they were configured on a separate physical switch.

114

參考答案

IP addresses (192.168.1.100) are represented as a string of four decimal numbers separated by a period or a dot. This layout is also referred to as the dotted-decimal format.

115

參考答案

There are several types of networks, categorized based on their scale, functionality, and technologies: - LAN (Local Area Network): - A small network that typically spans a single building or a campus, designed to connect computers, printers, and other devices in close proximity. - Example: A home network or an office network. - WAN (Wide Area Network): - A network that connects devices over a large geographical area, such as across cities, countries, or continents. - Example: The Internet or a multinational corporation's network. - MAN (Metropolitan Area Network): - A network that covers a city or a large campus, bridging the gap between LANs and WANs. - Example: A city's broadband network or a university campus network connecting multiple buildings. - PAN (Personal Area Network): - A network designed for personal devices like smartphones, tablets, laptops, or wearable devices. It typically operates within a range of a few meters. - Example: Bluetooth networks or Wi-Fi networks used for personal devices. - VPN (Virtual Private Network): - A network that enables secure, encrypted communication over the Internet, allowing remote users to connect to a private network as if they were on-site. - Example: A corporate employee accessing their office network from home. - CAN (Campus Area Network): - A network that connects a group of LANs within a specific geographical area, typically across a campus or business complex. - Example: A university connecting multiple departments within a single campus. - SAN (Storage Area Network): - A specialized network designed for high-speed data transfer and storage management, connecting servers with storage devices. - Example: Data centers that require fast and secure access to large volumes of data. Each type of network serves a specific purpose depending on its size, scope, and intended use.

116

參考答案

Hubs are fairly basic and not particularly intelligent devices. Any signal received on any port is transmitted/repeated out every other port inside the Hub.

117

參考答案

A VLAN (Virtual Local Area Network) is a logical subdivision of a network that creates distinct broadcast domains within a single physical network infrastructure. This logical partitioning enhances security by isolating critical data and devices, boosts network performance by minimizing broadcast traffic, and offers superior network management and adaptability. This is achieved by organizing devices based on their roles instead of their physical proximity.

118

參考答案

A proxy server acts as an intermediary between a client and the internet. It forwards client requests to external servers, providing anonymity and enhancing security. By caching content, a proxy can also improve performance by reducing bandwidth usage and speeding up access to frequently requested resources.

119

參考答案

A router is a networking device that forwards data packets between different networks, typically between a local network (LAN) and the Internet (WAN). Routers play a crucial role in directing traffic efficiently, ensuring data reaches its destination across multiple networks. Functions of a Router: - Routing: Routers use routing tables and algorithms to determine the best path for data packets to travel across different networks. - Network Address Translation (NAT): Routers often perform NAT to allow multiple devices on a local network to share a single public IP address. - Traffic Management: Routers manage network traffic and can prioritize certain types of traffic (e.g., VoIP or streaming video) to ensure better performance. - Security: Routers often include built-in firewall features to protect the local network from external threats. - Interconnectivity: Routers allow communication between devices on different subnets or networks, such as connecting a home network to the Internet. In essence, a router is the "traffic director" of a network, ensuring that data flows to the right destinations efficiently.

120

參考答案

The client is the component responsible for initiating communication and requesting a network service, such as retrieving a web page, transferring a file, or transmitting an email. The server is the component responsible for responding to client requests and delivering the requested service, such as transmitting a webpage, file, or email. Computer application uses the client-server model.

121

參考答案

You should first check these things: - Bandwidth utilization - Broadcast storms - Duplex mismatch - High CPU usage on network devices - Excessive downloads or streaming - Malware or abnormal traffic You can use tools such as: - Wireshark - SNMP monitoring - NetFlow - Interface statistics on switches/routers You should also check: " show interfaces show processes cpu"

122

參考答案

I've configured site-to-site and remote access VPNs. Security measures include encryption, authentication, and access controls.

123

參考答案

Proxy servers primarily prevent external users from identifying the IP addresses of an internal network. Without knowledge of the correct IP address, the physical location of the network cannot be determined. This makes network locations more secure. Proxy servers can also make a network invisible to external users.

124

參考答案

TCP is connection-oriented and reliable; use it for web traffic. Tip: When debugging, check retransmissions and RTT.

125

參考答案

SNMP stands for Simple Network Management Protocol. SNMP is a network protocol that allows data collection, organization, and transmission among network devices. SNMP is a prevalent tool in network management, utilized to configure various network devices such as hubs, servers, routers, printers, and switches. Critical components of SNMP are: - Management Information Base (MIB) - SNMP Manager - SNMP Agent - Managed device

126

參考答案

A forward lookup translates domain names into IP addresses, enabling browsers to locate web servers. Conversely, a reverse lookup converts IP addresses back to domain names, often used for verifying server identities. Both functions are integral to maintaining reliable and secure internet operations.

127

參考答案

This question assesses candidate's big-picture thinking and future network planning capability. Strong answers will reference redundant links, failover systems, load balancing, and modular designs that can scale and grow along with the development of the company.

128

參考答案

STP (Spanning Tree Protocol) prevents switch loops by creating a loop-free logical topology.

129

參考答案

A stateless firewall filters individual packets based only on predefined static rule checks for source/destination IP, port, and protocol, and does not track active connection state. A stateful firewall tracks the full state of all active network connections, and only allows legitimate response packets that belong to an existing valid outgoing connection, providing far stronger security against unknown malicious incoming traffic.

130

參考答案

Both involve breaking down a message into manageable parts, addressing it to the correct recipient, and using a network to deliver it. With a letter, the message is the text on the paper, the address is the destination, and the postal service is the network. Similarly, on the internet, data is broken down into packets, each packet has an IP address for the destination, and routers act as the postal workers, directing the packets across the network. Just as a letter might pass through multiple postal offices, data packets may traverse several routers before reaching their final destination. Both systems rely on a standardized process to ensure delivery, although the internet uses protocols like TCP/IP to ensure reliable and ordered delivery of packets, which is more sophisticated than the basic letter system.

131

參考答案

We can find port number using command line Tool, and using resource monitor. By utilizing the tools like ‘Netstat' we can troubleshoot and monitor our system and network, and also gain the insights into network security, and identify any processes using specific ports. It will help us in managing and securing our system efficiently.

132

參考答案

Virtual Local Area Networks (VLANs) are fundamental in segmenting a network into logical groups, you can explain as below: - Definition: A VLAN is a logical grouping of devices in the same broadcast domain, regardless of their physical location. VLANs are configured on Layer 2 switches to create separate networks within a physical network. - Configuration: The steps to create and assign a VLAN on a switch: 1. Use the command vlan to create the VLAN. 2. Assign the VLAN to ports using switchport access vlan . 3. Configure inter-VLAN routing if devices in different VLANs need to communicate (using a router or Layer 3 switch). - Benefits: VLANs improve network security by isolating sensitive data, reduce broadcast traffic, and increase network performance by limiting the size of collision domains.

133

參考答案

This layer ensures reliable data transfer between devices on the same network segment. It organizes data into frames and checks for errors using techniques like MAC addressing.

134

參考答案

A collision domain is an area of an Ethernet network where collisions can occur. If one station can prevent another from sending because it uses the network, they are in the same collision domain. It mostly happens when multiple devices are connected through a hub or repeater.

135

參考答案

You are expected to explain the definition of layer 2 Trunk port, the feature that it carries multiple VLAN tagged traffic, and its common usage scenarios on switch interconnection.

136

參考答案

I regularly read industry publications, attend webinars and conferences, participate in online forums, and pursue relevant certifications. I also experiment with new technologies in lab environments to gain hands-on experience.

137

參考答案

VLANs (Virtual Local Area Networks) segment networks to improve performance and security. They achieve this without the need for new hardware. They allow logical grouping of devices regardless of physical location.

138

參考答案

You are expected to explain the full name of Infrastructure as Code, the technology that you can define and deploy all cloud infrastructure and network resources via human readable code template instead of manual operation on web console.

139

參考答案

To add data items in checksum calculations, one's complement arithmetic is used.

140

參考答案

Subnetting divides IP address ranges into smaller segments. I determine subnet masks based on the number of required subnets and hosts.

141

參考答案

This question is ideal for when you're trying to understand the candidate's expertise in network security and risk management. Answer sample: Evaluating the security posture of a network is a multifaceted process that requires a comprehensive approach. I employ various methodologies and tools for penetration testing and vulnerability assessments to ensure the robustness of our network security measures. One key methodology I use is penetration testing, which involves simulating real-world cyber attacks to identify potential vulnerabilities and assess the effectiveness of our defensive measures. I often conduct both internal and external penetration tests, leveraging automated tools like Metasploit and Burp Suite, as well as manual testing techniques to identify vulnerabilities that may evade automated scans. In addition to penetration testing, I regularly perform vulnerability assessments to proactively identify and remediate weaknesses in our network infrastructure. This involves using vulnerability scanning tools such as Nessus, OpenVAS, or Qualys to scan our network for known vulnerabilities in software, configurations, or system settings. These assessments provide valuable insights into areas of potential risk, allowing us to prioritize remediation efforts based on the severity and impact of identified vulnerabilities.

142

參考答案

Your browser starts by looking up the website's real address. The name you type is not the actual location. DNS servers translate this name into a numerical IP address. Next, your browser creates a connection to that server. It utilizes the TCP protocol to establish a secure pathway for data transfer. This happens through a three-way handshake process. Your browser then requests the webpage. It sends an HTTP message requesting specific content from the server. This message includes details about what your browser can handle. The server handles this request, and it responds by transmitting the webpage files. The latter consists of HTML, CSS, JavaScript code, and graphics. The files flow back to your device via the internet. Your browser receives all of these components. It reads the code, applies the styling, and executes the scripts, displaying all on your screen as one whole web page.

143

參考答案

Quality of Service (QoS) prioritizes network traffic based on importance, ensuring that critical applications like voice or video get sufficient bandwidth. To configure QoS, we classify traffic based on protocols or IP addresses and assign priority levels. This can be done on network devices like routers or switches, using policies like traffic shaping, policing, and scheduling to optimize bandwidth use.

144

參考答案

Network emergencies happen occasionally, the team needs someone who can think critically and stay calm under these situations. Qualified candidates should communicate clear task prioritization rules based on business impact and service dependencies. Great answers may reference formal incident response protocols.

145

參考答案

A straight-through cable has an identical pin connection at both ends. And that is the reason it used to connect two different devices—for example, a computer with a switch or a hub. On the other hand, a crossover cable has the pin connection reversed between the two ends, and it is mainly used to connect two similar devices, for example, two computers.

146

參考答案

These are private ip addresses. - Class A: 10.0.0.0 — 10.255.255.255 - Class B: 172.16.0.0 — 172.31.255.255 - Class C: 192.168.0.0 — 192.168.255.255

147

參考答案

A firewall acts as the first line of defense by filtering incoming and outgoing network traffic based on predefined security rules. It helps prevent unauthorized access and protects sensitive data from potential threats. I routinely configure and update firewall policies to adapt to evolving security risks.

148

參考答案

An IP (Internet Protocol) address is a unique identifier assigned to devices on a network, allowing them to communicate. IPv4 and IPv6 are two types of IP addressing protocols: - IPv4: Uses a 32-bit address format, allowing for approximately 4.3 billion unique addresses (e.g., 192.168.0.1). - IPv6: Uses a 128-bit address format, supporting around 340 undecillion unique addresses (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). IPv6 was developed to address the exhaustion of IPv4 addresses and supports features like auto-configuration and improved security.

149

參考答案

Benefits of using the Modem: - Modems are devices that allow two computers to communicate with each other. - Most modems come with a built-in router and firewall. - Modems mostly come free with the Internet service you take at home. - The modem is widely used in homes and small offices, and it is the simplest way to connect to the Internet.

150

參考答案

You are expected to describe the full troubleshooting workflow to locate the root cause of MPLS WAN link congestion, and give the corresponding resolution measures.

151

參考答案

The session layer manages communication sessions between devices. It establishes, maintains, and terminates connections as needed.

152

參考答案

NFV (Network Functions Virtualization) virtualizes network functions like firewalls and routers to reduce hardware dependency.

153

參考答案

A mesh network is a network topology where each node is connected to every other node directly (physically or virtually). Mesh networks are self-healing and highly redundant; if one of the primary paths is lost, data can reroute using other available paths. There are different types of mesh networks, and the most common ones are partial mesh and full mesh. In Partial Mesh topology, most of the devices are connected with each other, but few devices are connected with just two or three devices. In Full Mesh topology, every device is connected directly with every other device.

154

參考答案

I've found that switches play a vital role in improving network performance by intelligently forwarding traffic based on MAC addresses. When a switch receives a frame, it examines the source MAC address and adds it to its MAC address table, associating it with the port on which the frame was received. This process is known as MAC address learning. By learning and maintaining a MAC address table, a switch can make intelligent forwarding decisions, sending frames only to the intended recipients instead of broadcasting them to all connected devices. This helps reduce network congestion and improve overall performance. In my experience, understanding how switches learn MAC addresses and use them to forward traffic is essential for designing and troubleshooting efficient and secure networks.

155

參考答案

This question evaluates a candidate's ability to manage vendor relationships, negotiate contracts and make strategic decisions.

156

參考答案

A proxy server takes on the responsibility of accessing and retrieving data on behalf of users, much like how a DNS server caches website addresses. Additionally, it keeps a record of websites, distinguishing between those that are whitelisted or banned, thereby shielding users from easily avoidable viruses.

157

參考答案

The ping command checks the connectivity and latency between two devices in a network.

158

參考答案

Candidates should describe their mature method for assessing task urgency and importance, and explain how they balance immediate urgent needs with long-term planned network projects.

159

參考答案

• Identify and isolate the affected segment. • Check for hardware or software bottlenecks. • Use tools like traceroute and ping to diagnose the issue. • Optimize routing or increase bandwidth.

160

參考答案

TCP offers reliable, connection-oriented communication, while UDP provides faster, connectionless communication. Selection depends on application requirements.

161

參考答案

NAT translates private IP addresses to a single public address for internet access. I configure NAT rules on routers or firewalls to conserve IP addresses.

162

參考答案

DNS, or Domain Name System, translates human-readable domain names (like www.example.com) into IP addresses that computers use to identify each other on the network. This service simplifies navigation and ensures users can access websites without needing to remember numerical IP addresses.

163

參考答案

Any device that forwards frames based on their Layer-2 MAC addresses using Ethernet. While a hub repeats all frames to all ports, an Ethernet switch forwards frames only to the ports for which they are destined. An Ethernet switch creates a collision domain on each port, while a hub generally expands a collision domain through all ports.

164

參考答案

If you've previously worked as a Network Engineer, summarize your experience. If not, discuss relevant skills and projects and how they'll relate to your day-to-day activities on the job. Looking over your resume will help you prepare for this question. Note the highlights so you can be ready to talk about them if asked to do so. You'll also want to include information that's not listed on your resume. Otherwise, it may sound like you're just repeating those details. Instead, discuss what you learned in previous positions and how those experiences relate to your current skill set. You can also mention any relevant courses you've taken or certifications you've earned.

165

參考答案

I manage network device configurations and backups by using configuration management tools and automated backup solutions. This includes regularly backing up device configurations, maintaining version control, and storing backups in secure locations. Regular audits and updates ensure that configurations are up-to-date and can be quickly restored in case of device failures or configuration errors.

166

參考答案

You can design this architecture with 2 tiered ALBs with NLBs and CDNs, with Infrastructure as Code for disaster recovery, to support distributed global user access with high availability and low latency.

167

參考答案

Orthogonal Frequency Division Multiplexing (OFDM): It is also the multiplexing technique that is used in an analog system. In OFDM, the Guard band is not required and the spectral efficiency of OFDM is high which oppose to the FDM. In OFDM, a Single data source attaches all the sub-channels.

168

參考答案

You secure network devices by implementing AAA (Authentication, Authorization, Accounting) to centralize access control and audit all user actions, using SSH instead of unencrypted Telnet for remote management sessions, and deploying Access Control Lists (ACLs) to filter unauthorized incoming and outgoing traffic to device management interfaces and sensitive network segments.

169

參考答案

A MAC (Media Access Control) address is a unique identifier assigned to a network interface card (NIC) for communication within a local network. It operates at the data link layer. An IP (Internet Protocol) address, on the other hand, identifies devices across different networks and operates at the network layer. MAC addresses are permanent, while IP addresses can change.

170

參考答案

The following are some of the important reasons for using MAC addresses: - First, it provides a secure way to find senders or receivers in the network. - The MAC address is useful in preventing unauthorized network access. - MAC address is a unique number and can be used to track the device. - Wi-Fi networks at the airport use the MAC address of a specific device to identify it.

171

參考答案

I have extensive experience with wireless networking, including designing and deploying Wi-Fi networks, configuring access points and controllers, and optimizing wireless coverage and performance. I use tools like Ekahau and AirMagnet for site surveys and spectrum analysis. Additionally, I implement security measures such as WPA3 encryption and network segmentation to protect wireless networks from unauthorized access.

172

參考答案

One main issue with larger businesses is security. If the business hosts its own web host servers, you must understand how to protect the internal network from outside Internet traffic. Other issues include user management and desktop audits and inventory. You must be able to manage several desktops and servers at once.

173

參考答案

Describe the network issue and its impact. Explain your role and contributions within the team. Highlight the resolution process and the outcome. Example Answer: Our team faced a critical network outage affecting multiple departments. I coordinated with colleagues to systematically isolate the issue, ultimately identifying a misconfigured router. Together, we resolved the problem within hours, restoring full network functionality.

174

參考答案

While both routers and gateways perform similar tasks of forwarding data between networks, they have distinct roles in a network: - Router: - A router is a device that connects multiple networks (typically a local network to the Internet) and directs data packets between them. It makes forwarding decisions based on IP addresses and routing tables. - Routers operate at the Network Layer (Layer 3) of the OSI model and use routing protocols (e.g., OSPF, BGP, RIP) to determine the best paths for data. - Routers can perform tasks such as NAT (Network Address Translation) to allow private IP addresses on a local network to communicate with external public networks. - Gateway: - A gateway is a more general device that connects two different types of networks, often with different communication protocols. It acts as a translator or "bridge" between different network architectures, protocols, or even different network layers. - Gateways can operate at any layer of the OSI model, from Layer 3 (Network) to Layer 7 (Application), and are capable of performing more complex protocol conversions (e.g., converting from IPv4 to IPv6). - A default gateway is typically a router that connects a local network to external networks (such as the Internet). Key Difference: - Router: Routes data based on IP addresses between networks, operates at Layer 3. - Gateway: More versatile, can connect networks with different protocols and can operate at any OSI layer.

175

參考答案

You resolve MTU (Maximum Transmission Unit) and fragmentation issues by standardizing consistent MTU sizes across all network links, enabling Path MTU Discovery (PMTUD) to dynamically find the largest supported MTU along a path to avoid fragmentation, and configuring ICMP unreachable messages to not be blocked by intermediate firewalls to ensure PMTUD functions correctly.

176

參考答案

Maps IPv4 addresses to MAC addresses on LANs. Tip: Clear ARP cache to test MAC flapping.

177

參考答案

Most network admins need to work as a team. The interviewer will ask you questions regarding team environment to make sure you are comfortable working with other team members. Some people cannot work in a team and need to be in their own environment. If the company has a large network, however, you will probably need to work as a team with other engineers.

178

參考答案

The OSI model (Open Systems Interconnection model) is foundational in networking, as it breaks down the complexities of network protocols into seven layers. You can describe the seven layers and their purpose as below: - Layer 1: Physical – Deals with hardware and transmission media (e.g., cables, switches). - Layer 2: Data Link – Manages data transfer between devices on the same network (e.g., Ethernet). - Layer 3: Network – Handles routing and addressing (e.g., IP, routers). - Layer 4: Transport – Ensures reliable data transfer (e.g., TCP, UDP). - Layer 5: Session – Manages sessions between applications. - Layer 6: Presentation – Formats data for the application layer (e.g., encryption, compression). - Layer 7: Application – Interface for end-user applications (e.g., HTTP, FTP).

179

參考答案

When information needs to be broken down into smaller, more manageable bits before being sent across the network, it is called data encapsulation. The source and destination addresses, as well as parity checks, are included in this process. This helps ensure that the information remains intact during transmission over the network.

180

參考答案

SD-WAN (Software-Defined Wide Area Network) uses software for centralized management of WAN resources, optimizing performance.

181

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It's important you can communicate to the interviewer the various network engineering skills you possess. When answering this question, you could mention the more technical skills you're equipped with, like your ability to troubleshoot hardware and software various types of network infrastructure issues as well as soft skills like organisational skills and your ability to manage projects on time. Example response: "I have the technical, analytical, and problem-solving skills to troubleshoot network problems and resolve issues quickly and efficiently with little to no downtime for the end user."

182

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A VLAN is a 'Virtual Local Area Network.' It is a group of devices within a network, regardless of the physical location. It allows network administrators to segregate traffic, enhance security by isolating sensitive data, and reduce congestion by limiting broadcast traffic to devices within the same VLAN. VLANs improve network efficiency and simplify management.

183

參考答案

Subnetting divides a large network into smaller, more manageable subnetworks. It enhances network performance and security by reducing traffic and isolating segments. Subnetting also conserves IP addresses, making network management more efficient and scalable.

184

參考答案

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are both protocols used for sending data over the internet, but they differ in their approach. TCP is connection-oriented, meaning it establishes a connection before sending data, ensures reliable delivery using acknowledgements and retransmissions, and provides ordered delivery. UDP, on the other hand, is connectionless; it sends data without establishing a connection first, offering faster transmission speeds but without guaranteed delivery or order. In summary, TCP is reliable but slower, suitable for applications like web browsing and file transfer where data integrity is paramount. UDP is faster but unreliable, making it suitable for applications like streaming and online gaming where speed is more important than perfect data delivery.

185

參考答案

Pipelining is a term used to describe the sequence in which processes are carried out. Sequencing is the term used to describe the process of starting a new task before completing an existing job.

186

參考答案

A mesh network consists of multiple interconnected nodes that work together to provide seamless Wi-Fi coverage over a large area. Each node communicates with the others, forming a robust and flexible network. This setup eliminates dead zones and ensures consistent connectivity by dynamically routing data through the best available path.

187

參考答案

To diagnose performance issues, I start by checking bandwidth utilization using tools like NetFlow. I then analyze latency through ping tests and traceroutes to identify bottlenecks. Additionally, monitoring tools can help detect unusual traffic patterns or packet loss, guiding me to the root cause.

188

參考答案

RIP, or Routing Information Protocol, is used by routers to send data from one network to another. It effectively manages routing data by broadcasting its routing table to all other routers within the network.

189

參考答案

A LAN cable (Local Area Network cable) is a type of cable used to connect devices like computers, routers, switches, and other network equipment within a local area network (LAN). The most common type of LAN cable is Ethernet cable, which uses twisted pair wiring and an RJ45 connector to establish wired network connections. Types of LAN Cables: - Ethernet Cable (Twisted Pair): These cables use pairs of insulated copper wires twisted together to reduce interference. The most common types are: - Cat5e (Category 5 enhanced): Supports speeds up to 1 Gbps over short distances (up to 100 meters). - Cat6 (Category 6): Supports speeds up to 10 Gbps over shorter distances (up to 55 meters). - Cat6a (Category 6 augmented): Supports 10 Gbps over longer distances (up to 100 meters). - Fiber Optic Cable: Used for longer-distance connections and higher bandwidth, fiber optic cables use light to transmit data and are often used for backbone connections in larger networks. Ethernet cables are the most commonly used LAN cables in networking due to their reliability, cost-effectiveness, and ease of installation.

190

參考答案

Bash helps automate repetitive actions on Unix-based systems and simplifies tasks like configuring network interfaces, managing firewall rules, and performing routine maintenance.

191

參考答案

Disadvantages of star topology include:- - It has a single point of failure; if the central hub fails, everything connected to it will fail. - It is costly to manage, as you need a high-end hub to cater to all traffic from the slave nodes. - It is not suitable for heavy network traffic. Because everything is connected to the hub, and if the hub is not working properly, it slows down the entire network.

192

參考答案

Advantages of Piggybacking: The major advantage of piggybacking is the better use of available channel bandwidth. Disadvantages of Piggybacking: The major disadvantage of piggybacking is additional complexity and if the data link layer waits too long before transmitting the acknowledgment, then re-transmission of the frame would take place.

193

參考答案

Four protocols are managed by this layer: ICMP, IGMP, IP, and ARP.

194

參考答案

You are expected to explain the permission differences, access functions, switching methods of User mode, Privileged mode, Global Config mode on Cisco IOS router.

195

參考答案

Using a blend of tools and metrics allows you to maintain a pulse on network performance and health. Here are some of the most common ones (Keep in mind this answer will vary as there are many tools; the idea is that candidates are able to answer with their own toolkit and why they use it): Performance Monitoring Tools - Network Performance Monitors (NPMs): Tools like SolarWinds, Nagios, and PRTG Network Monitor offer real-time visibility into the performance of network devices and traffic patterns. They can track metrics such as bandwidth usage, packet loss, and latency. - Protocol Analyzers: Wireshark is a widely used protocol analyzer that helps in inspecting the details of network traffic at a granular level. It is instrumental in identifying anomalies and inefficiencies in data transmission. - Speed Test Tools: Tools such as Ookla's Speedtest provide quick assessments of internet connection speed, including download and upload speeds, which are critical for troubleshooting performance issues. Key Metrics for Network Health: - Bandwidth Utilization: This metric measures the amount of data being transmitted over a network connection in a given time frame, helping identify bottlenecks and ensure adequate bandwidth for critical applications. - Latency: Latency indicates the time it takes for a data packet to travel from source to destination. High latency can significantly impact applications requiring real-time communication. - Packet Loss: Packet loss occurs when packets fail to reach their destination, which can degrade network performance and affect application reliability. Monitoring packet loss helps in pinpointing unstable connections or hardware issues. - Jitter: Jitter measures the variability in latency over time in a network. Consistent jitter can cause issues in voice-over IP (VoIP) and video streaming services. Security Assessment Tools: - Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS): These tools, such as Snort or Cisco's Firepower, monitor network traffic for suspicious activities that could indicate a security threat, providing alerts and, in the case of IPS, taking actions to block the threat. - Firewall Management Tools: Tools like FireMon and AlgoSec manage firewall rules and policies, ensuring that firewalls are effectively protecting the network without unnecessarily impeding performance. - Vulnerability Scanners: Tools such as Nessus or Qualys scan network devices for known vulnerabilities, helping administrators to patch potential security holes before they can be exploited.

196

參考答案

A VLAN (Virtual Local Area Network) is a logical grouping of devices on a network, allowing them to communicate as if they were on the same physical LAN, even if they're not. VLANs enable network segmentation, enhancing security and efficiency by isolating different departments or groups within the same physical network. For instance, VLANs can separate traffic from finance, HR, and IT, reducing broadcast traffic and improving network performance.

197

參考答案

I take a multi-layered approach to network security, including: - Implementing firewalls and intrusion detection/prevention systems - Segmenting networks using VLANs and access control lists - Encrypting sensitive data in transit and at rest - Regularly updating and patching systems - Conducting security audits and vulnerability assessments - Implementing strong authentication mechanisms - Educating users about security best practices

198

參考答案

From what I've seen, the primary difference between static and dynamic routing lies in how routes are determined and maintained within a network. In static routing, routes are manually configured by the network administrator, while in dynamic routing, routers automatically discover and maintain routes using routing protocols. Static routing can be a go-to choice when dealing with small networks, as it requires less overhead and provides more control over the routing process. However, it can be challenging to manage in larger networks, as any changes in the network topology require manual updates. On the other hand, dynamic routing is more suitable for larger networks or networks with frequently changing topologies. It can adapt to network changes automatically, reducing the administrative burden. However, it requires more resources and processing power to maintain routing tables and exchange routing information. In my experience, choosing between static and dynamic routing depends on the size, complexity, and requirements of the network. Each method has its advantages and drawbacks, and the best choice will depend on the specific network environment.

199

參考答案

To configure a router to allow traffic between two subnets: - Assign each interface on the router an IP address from the respective subnet. - Ensure routing is enabled so the router can forward packets between interfaces. - Set up static routes if needed or use dynamic routing protocols like OSPF. - Verify the interfaces are active and the routing table includes routes for both subnets. - Check firewall rules to ensure traffic is not blocked.

200

參考答案

Port numbers are used in networking to differentiate various services and applications that run on a single device. They act as logical endpoints for communication between devices on a network, allowing multiple services to run on a single IP address. Functions of Port Numbers: - Identification: Port numbers identify specific processes or services on a device. For example, HTTP uses port 80, while HTTPS uses port 443. - Multiplexing: Port numbers allow multiple services (such as web browsing, email, and file transfer) to coexist on the same IP address. Each service is assigned a unique port number. - Routing Data: When data is transmitted to a device, the port number tells the operating system which application or service should handle the data. Types of Port Numbers: - Well-Known Ports (0-1023): Assigned to widely used services like HTTP (80), FTP (21), and DNS (53). - Registered Ports (1024-49151): Assigned to less common but still recognized applications and services. - Dynamic or Private Ports (49152-65535): Used for temporary or private connections, often for client-side communication in protocols like HTTP or FTP. Port numbers are crucial for managing communication in networking protocols.

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