OSPF is one of the most popular routing protocols around. As a link state protocol however, when it comes to route filtering, it has some quirks that should be considered when deploying it. Unlike its distant cousins EIGRP and RIP, OSPF routes can only be filtered at the border of an OSPF area. In this […]
About Lazaros Agapidis
Lazaros Agapidis is a Telecommunications and Networking Specialist with over twenty years of experience.
He works primarily with IP networks, VoIP, Wi-Fi, and 5G, has extensive experience in training professionals for Cisco certifications, and his expertise extends into telecommunications services and infrastructure from both an enterprise and a service provider perspective.
In addition to his numerous vendor certifications, Lazaros has a solid online presence as an expert in his field, having worked in both public and private sectors within North America and in Europe.
He has enjoyed sharing his practical experiences in writing as well as through engaging online training.
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EIGRP Metric and K Values Explained
If you’ve used EIGRP at all, then you’ve probably already heard about its metric formula and the related K values that are used to measure the distance of a particular path to a destination network. It’s not always easy to get your head around these concepts and how they’re used in the context of this […]
What is Cisco FHRP (First Hop Redundancy Protocol) Explained With Diagrams
When you configure a host with network parameters, one of the elements that you configure is the default gateway. But what happens if the device acting as the default gateway fails? Isn’t that a single point of failure? Well, yes, it is. To mitigate such failures, we can use what is known as a First […]
Description & discussion of OSPF Stub Areas-What They Are and Use Cases
OSPF (Open Shortest Path First) stub areas are specialized regions within an OSPF network designed to simplify routing and improve efficiency. By limiting the type of external routes that can be propagated into these areas, stub areas reduce the amount of routing information each router must process. This configuration is particularly beneficial in large or […]
Cisco Embedded Packet Capture (EPC) – Explanation & Configuration
Troubleshooting network performance can sometimes be challenging, especially if the problem being faced is intermittent, or if it results in the degradation of network performance. There is a whole arsenal of tools out there that can help in diagnosing and resolving such network issues. Cisco IOS and IOS-XE devices have an embedded feature that allows […]
Explanation and Discussion of Gratuitous ARP (GARP) in Networks
Address Resolution Protocol (ARP) is a fundamental protocol used in IPv4 networks. Its primary function is to resolve a device’s IP address to its physical MAC address. Gratuitous ARP, or GARP, is a special kind of ARP message that’s used for specific purposes. In this article, we’ll take a closer look at GARP, examine how […]
EIGRP Variance and Unequal Cost Load Balancing in Networking
EIGRP is an advanced routing protocol that was originally developed by Cisco, but has since been adopted by other vendors as well. Along with OSPF, it is one of the most popular Interior Gateway Protocols (IGPs) used by large enterprises for the internal routing of their networks. One of the advantages that EIGRP has over […]
Classful vs Classless IP Addressing – Comparison and Differences
Classful and Classless addressing are two methodologies used in the allocation and identification of IP addresses within the Internet Protocol Version 4 (IPv4) framework. Classful addressing, which was the initial scheme, divides the IP address space into classes which determines each network’s size and its division between network and host identifiers. In contrast, classless addressing […]
What is SNMP (Simple Network Management Protocol) in Networking
Simple Network Management Protocol (SNMP) is a widely used protocol for managing and monitoring network devices on IP networks. It enables network administrators to manage network performance, find and solve network problems, and plan for network growth. In this article, we’ll take an introductory look at the protocol, see how it works, and we will […]
What is Link Aggregation (LAG) in Networking?
Link aggregation is a technique used in networking to bundle multiple physical ports on a network device to operate as a single link. The aggregated link acts as a single logical port functioning at a speed equal to the sum of the bandwidths of all of the physical links. In this article, we’ll further explore […]
How Does a Network Switch Learn MAC Addresses?
A switch is a network device that interconnects host devices at Layer 2 of the OSI model. In order to perform its function correctly, it must be able to learn the MAC addresses of the connected hosts and maintain them in a MAC address table. In this article, I’ll explain in detail how a switch […]
Introduction to Cisco EEM (Embedded Event Manager)
Cisco’s Embedded Event Manager (EEM) is a powerful tool that can be configured to detect specific events and respond to those events in specific ways. EEM was introduced in the early 2000s and is one of the earliest attempts at network automation. Even so, it is still used extensively today and remains a versatile tool […]
Comparison of Reported Distance vs Feasible Distance in EIGRP
One of the concepts involved with the EIGRP routing protocol that can sometimes be confusing is the idea of the feasible distance and the reported distance of a particular network destination. Understanding these two measurements of EIGRP is an important step in understanding some of the fundamental mechanisms of EIGRP. Definition of Terms Let’s start […]