Month: September 2019

Network topology diagram in Cisco Packet Tracer showing routers, switches, servers, and laptops. Laptop0 displays a DHCP failure message with APIPA fallback.
CCNA September 30, 2019

What is DHCPv4 Relay?

In enterprise networks, dedicated servers are usually used to provide DHCP, DNS, TFTP, and FTP services. The clients are not generally on the same subnet as those servers. The clients used to broadcast messages to locate the servers and get services. Now, look at the figure below. Laptop0 is attempting to acquire an IPv4 address […]
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Diagram illustrating DHCPv4 server configuration and verification with a Cisco router and DHCP client.
CCNA September 29, 2019

Master DHCPv4 Server Configuration (Updated 2025)

A Cisco router can be configured as a DHCPv4 server. The DHCPv4 server assigns and manages IPv4 addresses from specified address pools within the router to DHCPv4 clients. The steps for configuring the DHCPv4 server on Cisco routers are the following: Excluding IPv4 Addresses The router configured as the DHCPv4 server assigns all IPv4 addresses […]
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DHCPv4 message format table showing fields like OP Code, CIADDR, YIADDR, and DHCP options with bit lengths.
CCNA September 28, 2019

Understanding DHCPv4 Message Format

Dynamic Host Configuration Protocol version 4 (DHCPv4) is a cornerstone of IP address management in IPv4 networks, automating the assignment of IP addresses, subnet masks, default gateways, and other network parameters. Based on the Bootstrap Protocol (BOOTP), DHCPv4 uses UDP ports 67 (server) and 68 (client) to exchange messages between clients and servers. This article […]
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Diagram illustrating the DHCPv4 process with a server offering an IP address to a client.
CCNA September 26, 2019

Understanding DHCPv4: A Comprehensive Guide

In modern networking, every device requires a unique IP address to communicate effectively. Understanding IP address management is crucial for network management. Static IP addresses are manually assigned to devices like routers, servers, and printers with fixed locations, enabling easy remote management. However, managing IP addresses for mobile or frequently changing devices is challenging, which […]
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Diagram illustrating the three-step process of configuring IPv6 ACLs, including creating a named ACL, using permit or deny statements, and applying to an interface.
CCNA September 22, 2019

Understanding IPv6 ACLs Configuration: Step-by-Step Guide

Access Control Lists (ACLs) are a fundamental component of network security, and understanding IPv6 ACLs is essential for CCNA and CCNP certification candidates. As networks transition from IPv4 to IPv6 to accommodate the growing number of devices, mastering IPv6 ACL configuration is critical for securing modern networks. This comprehensive guide explains IPv6 ACLs, compares them […]
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Understanding ACL Errors in Cisco Networks
CCNA September 22, 2019

How to Troubleshoot ACL Errors

Access Control Lists (ACLs) are fundamental to network security and traffic management in Cisco environments. However, misconfigurations can lead to ACL errors, blocking legitimate traffic or allowing unauthorized access. This article explores common ACL errors with examples, focusing on troubleshooting techniques using show commands. Understanding these errors is crucial for passing certification exams and excelling […]
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A clipboard with green checkmarks and red Xs next to the text "ACL Logics" on a blue background.
CCNA September 21, 2019

Inbound and Outbound ACL Logic

Access Control Lists (ACLs) are a fundamental component of Cisco networking, used to filter traffic based on predefined rules. For CCNA and CCNP students, mastering ACLs is critical for securing networks and passing certification exams. ACLs allow network engineers to permit or deny packets based on criteria like source and destination IP addresses, protocols, and […]
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Diagram illustrating Extended ACLs with permit and deny rules for IP ranges 192.168.2.0 and 192.168.2.123, showing network traffic control.
CCNA September 21, 2019

How to Configure Extended ACLs – Exclusive Explanation

The number of extended ACLs ranges from 100 to 199 and 2000 to 2699, providing 799 possible numbered ACLs. The 100-199 range was historically used, while 2000-2699 is recommended for modern networks due to greater flexibility and support for named ACLs. Choose based on your network’s complexity and Cisco IOS version. We can also create […]
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Illustration of social engineering with two silhouetted figures using a phone and laptop, surrounded by social media icons and lock symbols on a circuit-like background.
Cyber Security September 14, 2019

What Is Social Engineering in Cybersecurity? Types, Examples, and Prevention Strategies (2025 Guide)

Social engineering remains one of the most effective tactics in a cybercriminal’s arsenal, accounting for 36% of initial access vectors in incident response cases between May 2024 and May 2025. It’s a psychological manipulation technique where attackers exploit human behavior to gain unauthorized access to information, systems, or physical locations—without relying on code or exploits. […]
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Illustration of browser security threats featuring a globe icon, a masked hacker, and ad symbols on a blue background.
Cyber Security September 14, 2019

Browser Plugins and Poisoning: Risks, Exploits, and Defenses in Cybersecurity

Security backdoors and vulnerabilities can severely impact web browsers, leading to unwanted pop-up ads, collection of personal data, or installation of adware, viruses, or spyware. Cybercriminals often target a browser’s executable files, core components, and browser plugins to gain unauthorized access. Browser Plugins A browser plugin (now often called an extension or add-on in modern […]
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