Here's how you can ace technical interview questions in the network administration field.

Subnetting divides a large network into smaller subnets, enhancing performance and security by isolating device groups. Routers, switches, and hubs are key networking devices with distinct roles. Routers direct data packets between networks, finding the best path for data travel. Switches connect devices within a single network, using MAC addresses to forward data to the correct device. Hubs broadcast data to all devices in a segment, regardless of the destination. Data encapsulation involves breaking data into packets with headers for routing and reassembly. Packets travel across the network based on the OSI model, which has seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

For instance, if dealing with a connectivity problem, begin at the physical layer: check cables, connections, and hardware status. Next, move to the data link layer, examining switch and router configurations, followed by the network layer, ensuring proper IP addressing and routing. Continue through the transport layer, checking ports and protocols, up to the application layer, verifying software and services. Interviewers want to see your ability to use a systematic approach to solve problems, so demonstrating a clear, step-by-step troubleshooting methodology is crucial.

HTTP and HTTPS (which secure HTTP traffic) operate at the Application layer, facilitating web communication. FTP, also at the Application layer, is used for file transfers, while SNMP, at the same layer, manages network devices. TCP's handshake process, which establishes a connection through a three-step sequence (SYN, SYN-ACK, ACK) at the Transport layer. Additionally, understanding the differences between IPv4 and IPv6 addressing, such as address length and format, is crucial. Being able to explain these protocols and their mechanisms demonstrates your comprehensive theoretical and practical networking knowledge.

Securing a network from various threats involves implementing multiple layers of defense to maintain data integrity and confidentiality. One of the first steps is configuring robust firewalls to block unauthorized access and filter traffic based on security rules. Access control lists (ACLs) are essential for ensuring only authorized users can access specific parts of the network. Utilizing VPNs is crucial for encrypting data transmitted over the network, particularly for remote access, which secures communication channels and protects data from eavesdropping. Establishing a DMZ (Demilitarized Zone) adds another layer of security by isolating public-facing servers, such as web and email servers, in a separate network segment.

Software-Defined Networking (SDN) provides greater flexibility and control over network resources by decoupling the control plane from the data plane, allowing network administrators to manage network traffic more dynamically through centralized control software. This architecture enables the efficient routing of data, automated network management, and quick adaptation to changing network conditions or requirements. For example, SDN can optimize traffic flow based on real-time needs, improving performance and resource utilization. On the other hand, the proliferation of Internet of Things (IoT) devices introduces new security challenges due to their widespread deployment and often limited security capabilities.

Soft skills are important besides of technical abilities. You can evaluate both of them by a complex question. After checking the candidate’s tech background, one difficult question can make clear the candidate approach to answer, regardless of its knowledge. For example the way to ask you for details is important and also, how to present its opinion. Someone may avoid the main topic to cover the lack of knowledge, help them by saying: “I am not looking for your weakness, I am looking for your strength to extract the issue and finding the right way to the solution”. Ask them “If, for example, you were in front of a customer and this question was asked by him and you did not know the answer, how would you answer it?”