90+ 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

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

Network protocols like FTP, SSH, SSL, RDP, HTTPS are used for secure data transfer over a network.

• FTP (File Transfer Protocol) is used for transferring files between computers on a network.

• SSH (Secure Shell) is used for secure remote access to a computer or server.

• SSL (Secure Sockets Layer) is used for secure communication between web browsers and servers.

• RDP (Remote Desktop Protocol) is used for remote access to a computer's desktop.

• HTTPS (Hypertext Transfer Protocol Secure)...read more

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

I am currently working on Cisco ASA firewalls, Palo Alto firewalls, and F5 load balancers.

• Working on configuring and maintaining Cisco ASA firewalls for network security

• Configuring and managing Palo Alto firewalls for threat prevention and network security

• Managing and configuring F5 load balancers for traffic distribution and application security

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.

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

A personal computer communicates with a web application through a series of steps involving network protocols.

• The computer sends a request to the web application's server using the HTTP protocol.

• The server processes the request and sends back a response containing the requested information.

• The communication is facilitated by the TCP/IP protocol stack.

• Data is transmitted over the internet using IP addresses and domain names.

• Encryption protocols like HTTPS may be used to secure...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.

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

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

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

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

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.

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

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.

HA3 belongs to HMAC (Hash-based Message Authentication Code) and is used for secure authentication and integrity verification.

• HA3 stands for Hash-based Message Authentication Code 3

• It is used in cryptographic hash functions for secure authentication and integrity verification

• HA3 is commonly used in network security protocols such as TLS (Transport Layer Security) and IPsec (Internet Protocol Security)

The session table typically stores information about active network connections and their associated details.

• Contains information such as source and destination IP addresses

• Stores port numbers being used in the connection

• Tracks the protocol being used (e.g. TCP, UDP)

• May include timestamps for when the connection was established and last active

Firewall is a security system that monitors and controls incoming and outgoing network traffic, while a gateway is a node that connects two different networks.

• Firewall is a security system that filters network traffic based on predetermined security rules.

• Gateway is a node that acts as an entry and exit point for data between two networks.

• Firewall can be a software program or a hardware device, while gateway is typically a hardware device.

• Examples of firewalls include Cisco A...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

App ID in Palo Alto Firewalls is a feature that identifies applications on the network based on various parameters.

• App ID uses multiple methods to identify applications, including port-based, protocol-based, and application signature-based identification.

• It allows administrators to create policies based on specific applications rather than just ports or protocols.

• App ID helps in enhancing security by allowing granular control over application usage within the network.

• Examples...read more

I am flexible with shift timings and job location to ensure smooth operations and adaptability.

• I am open to working different shifts, including nights and weekends, to ensure 24/7 coverage for network security

• I am willing to relocate if necessary to take on new opportunities and challenges in different locations

• I understand the importance of being adaptable in the fast-paced field of network security

TCP and UDP are transport layer protocols used for communication between devices on a network.

• TCP (Transmission Control Protocol) is a connection-oriented protocol that ensures reliable data transmission by establishing a connection between two devices and providing error checking and flow control.

• UDP (User Datagram Protocol) is a connectionless protocol that does not establish a connection before transmitting data. It is faster but less reliable than TCP.

• TCP is used for appl...read more

I am currently working with Cisco ASA firewalls and Palo Alto Networks firewalls.

• Working with Cisco ASA firewalls

• Working with Palo Alto Networks firewalls

Types of IPSEC tunnels include Site-to-Site, Remote Access, and GRE over IPSEC.

• Site-to-Site: Connects two networks securely over the internet.

• Remote Access: Allows individual users to securely connect to a network from a remote location.

• GRE over IPSEC: Combines Generic Routing Encapsulation (GRE) with IPSEC for secure tunneling of non-IP protocols.

Public IP is the address assigned to a device that is visible on the internet. Local IP is the address assigned to a device on a local network.

• Public IP is unique and can be accessed from anywhere on the internet

• Local IP is used for communication within a local network

• Public IP is assigned by the Internet Service Provider (ISP)

• Local IP is assigned by the router or network administrator

• Examples of public IP: 216.58.194.174 (Google), 172.217.5.110 (YouTube)

• Examples of local IP:...read more

IP stands for Internet Protocol, which is a set of rules governing the format of data packets sent over a network. OSP refers to Open Shortest Path First, a routing protocol used in IP networks.

• IP is a protocol that defines how data is sent and received over a network.

• OSP is a routing protocol used to determine the best path for data packets to travel in an IP network.

• IP is a fundamental protocol in the internet protocol suite, while OSP is a specific routing protocol within ...read more

TLS Handshake is a process of establishing a secure connection between a client and a server.

• TLS Handshake involves a series of steps to establish a secure connection

• It includes negotiation of encryption algorithm, exchange of keys, and verification of digital certificates

• TLS Handshake ensures confidentiality, integrity, and authenticity of data transmitted over the network

• Examples of applications using TLS Handshake are HTTPS, SMTPS, FTPS, etc.

Heart Beat link is a feature in network security that ensures continuous communication between devices.

• Heart Beat link is a mechanism used to maintain a connection between two devices by sending periodic signals.

• It helps in detecting if a device is still active and reachable on the network.

• If the Heart Beat link fails, it can trigger alerts or actions to address the issue.

• Example: In a VPN connection, Heart Beat link can be used to ensure the tunnel remains open and active.

NAT is a technique used to map private IP addresses to public IP addresses for communication over the internet.

• NAT stands for Network Address Translation.

• It is used to conserve public IP addresses and provide security by hiding private IP addresses.

• There are three types of NAT: Static NAT, Dynamic NAT, and PAT.

• Static NAT maps a single private IP address to a single public IP address.

• Dynamic NAT maps multiple private IP addresses to a pool of public IP addresses.

• PAT (Port Addr...read more

To mitigate DOS and DDOS attacks, implement network security measures such as firewalls, intrusion detection systems, and rate limiting.

• Implement firewalls to filter out malicious traffic

• Use intrusion detection systems to detect and block suspicious activity

• Implement rate limiting to prevent overwhelming the network with excessive requests

PUSH flag is used to indicate the start of a new TCP session while URG flag is used to indicate urgent data.

• PUSH flag is set when a sender wants to push data to the receiver without waiting for a full buffer

• URG flag is set when a sender wants to indicate that some data is urgent and should be processed immediately

• PUSH flag is used to initiate a new session while URG flag is used to indicate the presence of urgent data within an existing session

VPN stands for Virtual Private Network. Site-to-site VPN allows multiple locations to securely connect over the internet.

• VPN creates a secure connection over the internet, allowing users to access a private network remotely.

• Site-to-site VPN connects multiple locations of a company securely over the internet.

• Site-to-site VPN uses IPsec (Internet Protocol Security) to encrypt data and ensure secure communication.

• Example: A company with offices in different cities can use site-t...read more

SSL persistence is a feature in F5 that allows a client to maintain a secure connection with the same server during a session.

• SSL persistence ensures that a client's SSL session is maintained with the same server throughout the session.

• This feature is useful in scenarios where multiple servers are used to handle client requests.

• SSL persistence can be configured based on SSL session ID, SSL session ticket, or SSL session match across multiple requests.

• For example, if a client ...read more

HA stands for High Availability and its prerequisites include redundancy, fault tolerance, and load balancing.

• Redundancy: Having duplicate components to ensure continuous operation in case of failure.

• Fault tolerance: Ability of a system to continue operating even in the presence of hardware or software failures.

• Load balancing: Distributing network traffic evenly across multiple servers to prevent overload.

• Prerequisites for HA include redundant hardware, failover mechanisms, a...read more

Upgrading OS in distributed mode requires careful planning and execution.

• Ensure compatibility of new OS with existing hardware and software

• Create a backup of all important data before starting the upgrade process

• Test the upgrade process in a non-production environment first

• Schedule the upgrade during a maintenance window to minimize disruption

• Monitor the upgrade process closely and have a rollback plan in case of issues

DNS infrastructure is a system that translates domain names into IP addresses to enable communication between devices on a network.

• DNS servers store records of domain names and their corresponding IP addresses.

• DNS resolution can be recursive or iterative.

• DNS cache is used to speed up the resolution process.

• DNSSEC is used to secure DNS infrastructure.

• DNS load balancing can be used to distribute traffic across multiple servers.

• DNS hijacking is a type of attack that redirects DN...read more

The VLANs used depend on the network architecture and requirements.

• VLANs are used to logically separate network traffic.

• They can be used to improve security and network performance.

• Common VLANs include management, voice, and data VLANs.

• The VLANs used depend on the network architecture and requirements.

• VLAN tagging is used to identify VLAN traffic on a network.

• VLANs can be configured on switches, routers, and firewalls.

Application override is a feature in network security that allows certain applications to bypass security policies.

• Application override allows specific applications to bypass firewall rules or other security measures.

• It is typically used for critical applications that may be blocked by default security settings.

• Administrators can configure application override rules to allow certain traffic to pass through the network without inspection.

• This feature can be useful for ensuring...read more

Port 443 is used for secure HTTP (HTTPS) communication over the internet.

• Port 443 is the default port for HTTPS traffic, which encrypts data using SSL/TLS protocols.

• It is commonly used for secure communication between web browsers and servers.

• HTTPS ensures that data transmitted over the internet is encrypted and secure.

• Many websites, such as online banking and e-commerce sites, use port 443 to protect sensitive information.

STP stands for Spanning Tree Protocol. It is used to prevent loops in a network and ensure redundancy.

• STP is a protocol used in network switches to prevent loops in a network.

• It ensures that there is only one active path between any two network devices.

• STP blocks redundant paths to prevent loops and ensures network redundancy.

• STP is important for network stability and preventing broadcast storms.

• Examples of STP variants include Rapid Spanning Tree Protocol (RSTP) and Multiple...read more