100+ Network Security Engineer Interview Questions and Answers

The protocols used in the transport layer of the OSI model are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

• TCP (Transmission Control Protocol) provides reliable, connection-oriented communication.

• UDP (User Datagram Protocol) provides unreliable, connectionless communication.

• TCP is used for applications that require guaranteed delivery of data, such as web browsing and email.

• UDP is used for applications that prioritize speed over reliability, such as s...read more

Firewalls are security devices that monitor and control incoming and outgoing network traffic based on predetermined security rules.

• Types of firewalls include: Packet Filtering, Stateful Inspection, Proxy Firewalls, and Next-Generation Firewalls.

• A firewall acts as a barrier between trusted and untrusted networks, preventing unauthorized access.

• Stateful firewalls track the state of active connections, while stateless firewalls treat each packet in isolation.

• Hardware firewalls ...read more

Understanding key concepts in network security: vulnerabilities, threats, risks, and principles of information security.

• Vulnerability: A weakness in a system (e.g., outdated software).

• Threat: A potential cause of an unwanted incident (e.g., malware).

• Risk: The potential for loss or damage when a threat exploits a vulnerability.

• Three principles of information security: Confidentiality, Integrity, Availability.

• IDs (Intrusion Detection Systems) monitor and analyze traffic; IPs (I...read more

The phases of site-to-site VPN are the steps involved in establishing and maintaining a secure connection between two networks.

• Phase 1: Authentication and key exchange

• Phase 2: Data encryption and tunnel establishment

• Phase 3: Traffic protection and monitoring

• Each phase has its own set of protocols and processes

• For example, in Phase 1, the VPN peers authenticate each other using methods like pre-shared keys or digital certificates

I recently troubleshooted a network security issue related to a firewall configuration.

• Identified the misconfigured firewall rule that was blocking legitimate traffic

• Reviewed firewall logs to determine the root cause of the issue

• Adjusted the firewall rule to allow the traffic and tested to ensure it was working properly

• Documented the issue and resolution for future reference

There are four types of logs in the monitor tab in Panorama.

• Traffic logs

• Threat logs

• URL logs

• Data logs

To configure a firewall from scratch, the first step is to define the security policy.

• Define the security policy based on the organization's requirements and compliance standards

• Identify the network topology and determine the zones that need to be protected

• Select the appropriate firewall hardware or software based on the requirements

• Configure the firewall rules to allow or deny traffic based on the security policy

• Test the firewall configuration to ensure it is working as inte...read more

Check the system logs for cluster failure in Paloalto firewall.

• Check the system logs for any error messages related to cluster failure

• Look for logs indicating cluster synchronization issues

• Review logs for any hardware or software failures in the cluster

Questions on router routing table, IPsec VPN types, application slowness troubleshooting, and F5 LTM.

• Router installs routes in routing table using routing protocols such as OSPF, BGP, etc.

• IPsec VPN types include site-to-site, remote access, and extranet VPNs.

• Application slowness troubleshooting involves checking network latency, server performance, and application code.

• F5 LTM questions may include load balancing algorithms, SSL offloading, and iRules scripting.

Site-to-site VPNs use key management protocols like IKE to establish secure tunnels with symmetric session keys.

• Key Management Protocols (KMP) like IKE (Internet Key Exchange) are used to negotiate and establish security associations.

• Symmetric session keys are generated for encrypting data, ensuring confidentiality during transmission.

• Protocols like IPsec often work in conjunction with KMPs to provide encryption and authentication for VPN tunnels.

• Example: IKEv2 is a widely us...read more

Firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules.

• Firewalls can be hardware, software or cloud-based

• Types of firewalls include packet-filtering, stateful inspection, proxy, and next-generation firewalls

• Packet-filtering firewalls examine packets and filter them based on source/destination IP address, port number, and protocol

• Stateful inspection firewalls track the state of network connec...read more

Nessus security tool provides vulnerability scanning and assessment capabilities for network security.

• Nessus can scan networks for vulnerabilities and provide detailed reports on security issues.

• It can identify misconfigurations, missing patches, and potential security threats.

• Nessus can prioritize vulnerabilities based on severity to help organizations focus on critical issues first.

SP3 Architecture of Palo Alto Firewalls refers to Security Processing Plane, Control Plane, and Data Plane.

• SP3 Architecture consists of Security Processing Plane (SP), Control Plane (C), and Data Plane (D)

• Security Processing Plane (SP) handles security functions like threat prevention and decryption

• Control Plane (C) manages routing and firewall policies

• Data Plane (D) processes and forwards traffic based on firewall policies

• SP3 Architecture helps in efficient and effective net...read more

A firewall filters traffic based on predetermined rules, while a next generation firewall includes additional features like intrusion prevention and application awareness.

• Firewall filters traffic based on IP addresses and ports

• Next generation firewall includes intrusion prevention, application awareness, and deep packet inspection

• NGFW can identify and block advanced threats like malware and ransomware

• NGFW can provide more granular control over applications and users

Routers are used to connect different networks while switches are used to connect devices within a network.

• Routers operate at the network layer (Layer 3) of the OSI model while switches operate at the data link layer (Layer 2).

• Routers can perform functions such as routing, filtering, and forwarding packets based on IP addresses.

• Switches are used to create a network by connecting devices such as computers, printers, and servers.

• Routers are necessary for connecting networks wit...read more

I troubleshoot the error, identify the root cause, implement a solution, and document the resolution for future reference.

• Identify the error message and troubleshoot the issue

• Review logs and system alerts to pinpoint the root cause

• Implement a solution to resolve the error

• Document the steps taken and the resolution for future reference

Methods to automate an existing network include scripting, configuration management tools, and network automation platforms.

• Use scripting languages like Python or Bash to automate repetitive tasks and configurations.

• Implement configuration management tools like Ansible, Puppet, or Chef to manage and automate network configurations.

• Utilize network automation platforms such as Cisco DNA Center or Juniper NorthStar to automate network provisioning, monitoring, and troubleshootin...read more

Types of ARP include ARP request, ARP reply, ARP probe, and ARP announcement.

• ARP request is used to find the MAC address of a device on the network.

• ARP reply is the response to an ARP request, providing the MAC address of the target device.

• ARP probe is used to check if an IP address is already in use on the network.

• ARP announcement is used to inform other devices on the network about a change in MAC address.

I have hands-on experience with various network security devices.

• Firewalls: Cisco ASA, Palo Alto, Fortinet

• Intrusion Detection/Prevention Systems: Snort, Suricata

• VPN: Cisco AnyConnect, OpenVPN

• Web Application Firewalls: ModSecurity, F5 ASM

• SIEM: Splunk, ELK

• Network Access Control: Cisco ISE, Aruba ClearPass

Yes, TCP Header Flags are used to control the flow of data between devices.

• TCP Header Flags are 6 bits long and are used to control the flow of data between devices.

• There are 6 TCP Header Flags: URG, ACK, PSH, RST, SYN, and FIN.

• URG is used to indicate that the data is urgent and should be prioritized.

• ACK is used to acknowledge receipt of data.

• PSH is used to push data to the receiving device.

• RST is used to reset the connection.

• SYN is used to synchronize sequence numbers.

• FIN is...read more

STP prevents loops in network topologies, while VTP manages VLAN configurations across switches.

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

• STP uses a root bridge election process based on bridge IDs to determine the best path.

• VTP (VLAN Trunking Protocol) allows switches to share VLAN information, simplifying VLAN management.

• VTP operates in different modes: Server, Client, and Transparent, affecting how VLANs are managed.

• Example: In a ...read more

TCP IP Header contains information such as source and destination IP addresses, port numbers, sequence numbers, and more.

• Source IP address

• Destination IP address

• Source port number

• Destination port number

• Sequence number

• Acknowledgment number

• Header length

• Checksum

DNS is a system that translates domain names to IP addresses. Network troubleshooting is the process of identifying and resolving issues in a network.

• DNS stands for Domain Name System and is used to translate domain names to IP addresses.

• Network troubleshooting involves identifying and resolving issues in a network to ensure smooth operation.

• Common network troubleshooting tools include ping, traceroute, and netstat.

• Examples of network issues include slow internet connection, ...read more

The OSI model is a conceptual framework used to describe network communication. It has 7 layers.

• Layer 1: Physical layer - deals with the physical aspects of transmitting data

• Layer 2: Data link layer - responsible for error-free transfer of data between nodes

• Layer 3: Network layer - handles routing and forwarding of data packets

• Layer 4: Transport layer - ensures reliable delivery of data between applications

• Layer 5: Session layer - establishes, manages and terminates connectio...read more

Privilege in Windows and Linux refers to the level of access and control a user or process has over system resources.

• Privilege levels in Windows are typically categorized as Administrator, Standard User, and Guest.

• In Linux, privilege levels are determined by user accounts and groups, with root being the highest level of privilege.

• Windows uses User Account Control (UAC) to manage privileges and prevent unauthorized changes.

• Linux uses sudo and su commands to elevate privileges ...read more

Network layers are a hierarchical approach to network communication, with each layer responsible for specific functions.

• There are seven layers in the OSI model: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

• Each layer performs specific tasks and communicates with adjacent layers to facilitate data transfer.

• For example, the Physical layer deals with the physical connection between devices, while the Application layer handles user interfaces an...read more

TCP/IP is a set of protocols used for communication between devices on the internet.

• TCP/IP stands for Transmission Control Protocol/Internet Protocol.

• Packet flow refers to the process of data being broken down into packets and transmitted across a network.

• Port numbers are used to identify specific applications or services running on a device.

• TCP/IP operates at the network and transport layers of the OSI model.

• Examples of TCP/IP protocols include HTTP, FTP, and SMTP.