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Stelios Antoniou

Stelios Antoniou (CCNA, NET+, MOUS) holds a BSc in Electronic Engineering and an MSc in Communication Networks. He has over three years of experience in teaching MS Office applications, networking courses and GCE courses in Information Technology. Stelios is currently working as a VoIP Engineer in a Telecom company, where he uses his knowledge in practice. He has successfully completed training on CCNP topics, Linux and IMS. His enthusiasm, ambition and knowledge motivate him to offer his best. Stelios has written many articles covering Cisco CCENT, CCNA, and CCNP.


Stelios Antoniou has written 59 posts for Pluralsight blog

EtherChannel Switch Link Aggregation

By Stelios Antoniou on April 11, 2012

Learn how to use EtherChannel to aggregate switch links in order to prevent packet loops in this networking how-to. Read more for an overview on link aggregation protocol (LACP) port aggregation protocol (PAgP), load balancing methods and more.


Using VRRP for Router Redundancy

By Stelios Antoniou on October 19, 2011

There are two popular options for providing redundancy at the network layer: HSRP and VRRP. However, VRRP is the only network layer redundancy protocol that can be used in a network with multivendor routers, which means it’s that much more important for you to learn about it.


CCNP TSHOOT: Using Cisco Troubleshooting Tools

By Stelios Antoniou on October 5, 2011

Learning the different Cisco troubleshooting tools is not only a requirement for the CCNP TSHOOT exam, but something every Cisco professional eventually needs to master. Learn about the basic Cisco troubleshooting tools and techniques and start utilizing them in your day to day network administration.


How to Prevent Loops with STP: Spanning Tree Protocol

By Stelios Antoniou on September 28, 2011

High availability is something both desirable and necessary. But sometimes, redundant links cause frame loops within a network that can lead to bandwidth and resource starvation. Learn how to use the Spanning Tree Protocol to prevent bridging loops and provide a loop-free network topology.


DHCP Troubleshooting

By Stelios Antoniou on September 14, 2011

Troubleshooting DHCP is something every network administrator will need to master. Mastering the Dynamic Host Configuration Protocol is required for the CCNP TSHOOT exam and will help you understand your IP infrastructure like never before.


How to Configure FreeSWITCH on Windows Part 3

By Stelios Antoniou on August 31, 2011

Our FreeSWITCH configuration series has reached it’s final stages. In this how-to you’ll learn how to configure your three FreeSWITCH dial-plan xml files: Public.xml, Default.xml, and Features.xml files so your PBX has the information for routing and terminating calls.


How to Configure FreeSWITCH on Windows Part 2

By Stelios Antoniou on August 24, 2011

As we continue our FreeSWITCH configuration series, learn some basic CLI FreeSWITCH commands, how to configure your VoIP Gateway and the basics on Regular Expressions, which you’ll need to know before configuring your Dial Plan.


How to Configure FreeSWITCH on Windows Part 1

By Stelios Antoniou on August 17, 2011

See how FreeSWITCH can fit into your network and what your basic configuration options are. We’ll go over how to create extension numbers, how to configure the Internal SIP Profile and how to test the client registration in FreeSWITCH.


How to Install FreeSWITCH in Windows

By Stelios Antoniou on August 10, 2011

FreeSWITCH is an open-standards VoIP telephony platform that is easy to install, configure and work with. And best of all, FreeSWITCH is free. Learn more about FreeSWITCH and how to install it on Windows.


How to Choose the Right VoIP Connectivity Solution

By Stelios Antoniou on March 30, 2011

Ready to make the move to VoIP? Learn about what the different VoIP connectivity solutions entail and which VoIP solution is right for your organization. We’ll examine simple VoIP connectivity, traditional PBX connectivity and IP PBX integration in your VoIP solution.


How to Prepare Your Network for VoIP

By Stelios Antoniou on March 16, 2011

Switching to VoIP (Voice over IP) can be a difficult task because there’s much to consider. This article will walk you through everything that you’ll need to consider before moving to VoIP including bandwidth, security, QoS, voice and data traffic separation, network resilience and high availability.


VoIP Architecture: VoIP Call Components

By Stelios Antoniou on June 23, 2010

Last time we went over the VoIP essentials including the benefits of VoIP and the fundamental VoIP terminology as well as the VoIP Protocols Now is a good time to introduce all the components that make Voice over IP a reality. Without them, IP telephony as we know it today wouldn’t exist. In this article […]


VoIP Signaling Protocols

By Stelios Antoniou on June 2, 2010

Now that you’re familiar with the VoIP essentials we can move on to VoIP protocols which are detailed in today’s article. Next time we’ll cover the VoIP Architecture, how to prepare your network for VoIP and how to activate VoIP which will get you to a good start with VoIP. Introducing VoIP Signaling Protocols Today […]


VoIP Essentials: The World of Packetized Voice

By Stelios Antoniou on May 11, 2010

Welcome to the new world of Packetized Speech! The voice infrastructure has been rapidly evolving during the last few years. Moving from traditional circuit switching to the packet switching technology has not been easy. The Internet and IP networks had to cope with the reliability and excellence of service of the Traditional TDM networks. Lot’s […]


The Best Way to Prepare For and Pass Your CCNA Exam

By Stelios Antoniou on July 14, 2009

I recently wrote an article for GoCertify outlining the best way to prepare for and pass your CCNA exam and I thought I’d share it with you here.   The article has three basic aims: 1. To guide you in choosing the appropriate training materials from which you will benefit the most based on the […]


Cisco Security: What You Need to Know About Network Attacks

By Stelios Antoniou on June 24, 2009

I’ve already introduced you to some of the most common network attacks like the IP address sweep, port scanning, and IP spoofing. I have also recently covered the ping of death and other network attacks, including the SYN flood, UDP flood, ICMP flood and the teardrop attack. Now that we have the basic Denial of […]


The PING of Death and Other DoS Network Attacks

By Stelios Antoniou on May 14, 2009

In my last article on How to Prevent Threats and Attacks on Your Cisco Network I explained in detail the various reconnaissance techniques that an attacker can exploit. Today I will focus on what is known as Denial-of-Service (DoS) Attacks. I’m very disappointed to admit that in our days this type of attack is one […]


How to Prevent Threats and Attacks on Your Cisco Network

By Stelios Antoniou on April 27, 2009

Most network attacks are well documented and investigated. The behavior of these attacks and the various stages that these attacks are progressing have already being examined and clarified. In this article I’ll provide you with all the necessary details concerning the behavior and attack strategy of the most dangerous malicious attacks that could invade your […]


Achieve Network Redundancy with the HSRP Protocol

By Stelios Antoniou on May 15, 2008

Reliability is an extremely important aspect in networking. A network that has been designed without the provision of redundancy is a network with a limited life span. Customers demand to have 100% service availability, while more and more time sensitive services are injected into networks such as voice and video over IP. These services need […]


How to Make Your Network Secure Using Secure Shell Protocol

By Stelios Antoniou on May 6, 2008

Nowadays, security is more important than ever. It’s extremely important that user accounts, passwords and hosts are protected from malicious attacks. Secure Shell Protocol (SSH) is capable of establishing secure encrypted tunnels for carrying data. SSH protocol can be used for remote access to your network devices, for securely transferring files between hosts and even […]