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VIP Perspectives

109 posts

QoS Mechanics

Posted by Sergey Feb 23, 2018

The topic of Quality of Service is absolutely huge. It is an entire universe in itself. I personally don't think I know QoS good enough. That's why it is a good idea to write about it!   First thing that hits you on the head when you start learning QoS concepts is the plethora of seemingly identical terms, each of which however presents a slightly different entity. Let's start with trying ... Read more


On the Shoulders of Giants

Posted by arteq Jan 26, 2018

This is a retrospective of those historically responsible for digital communication. These are the giants of our industry, the pioneers, the men, women, and corporations who created fire; our super novas. The systems they created are called networks. We call these legends, "Networkers."   Based on development by Jack Harrington and team at the Air Force Cambridge Research Center (AFCRC) in ... Read more

Introduction  All of the advanced features of BGP begin with establishing a BGP session between two BGP speakers. BGP in turn rides on TCP. As such, it is important to recognize and understand the symbiotic relationship between TCP and BGP and the intricate details of BGP session establishment as it relates to BGP’s use of TCP as a transport protocol. This blog aims to provide ... Read more

Introduction When boiled down to its basic parts, OSPF’s LSDB is much more simple than it appears. In reality, the LSDB is merely a listing of nodes and a description of the relationship between those nodes described using LSAs. Type-1 Router LSAs describe the router nodes in the network and their relationship to other nodes. Type-2 Network LSAs describe segments on the network where ... Read more

In June this year, Cisco launched their Software Defined Access (SDA), which is a solution in the intent-based networking space. There are also other players in this space, such as Apstra. What is intent-based networking, though?   Traditionally we have built networks with a imperative approach, meaning that we must precisely specify all of the components to end up with our desired state. ... Read more


BGP path selection

Posted by Sergey Sep 8, 2017

BGP is without question my favorite protocol! It is so powerful and flexible. It is unique, because it is the protocol that connects the biggest network on this planet so far: the Internet. And one of the most important topics in BGP is its path selection algorithm. For consistency, I'll use the term "prefix" to denote a route in BGP and the term "path" to denote a specific way this prefix can be ... Read more


Automating Cisco Using Ansible

Posted by Sergey Aug 10, 2017

Automation is definitely one of many buzz words going around in the networking world. I heard a few things about it, but until recently I didn’t have much idea about how it actually looks and feels. Then, a change came. A few months ago I was introduced to a wonderful configuration management platform called Ansible. The company I work for uses it to manage configuration of VMWare NSX ... Read more

Introduction  My intention with this blog post is to highlight a couple of scenarios that you are likely to face as a network engineer. Scenarios where it’s very important that you understand exactly what the words you choose to use actually mean to your co-worker. Whether it’s between a client or an internal discussion between network engineers and management – ... Read more


IP SLA Fundamentals

Posted by raymond Jun 13, 2017

Introduction Most of us, as network engineers, have been in a situation where users have reported performance issues with the network or that the network is down and we have to investigate to discover the root cause of the problem. When this happens, we usually rely on some sort of network monitoring and reporting application in order to get an idea of what our network is doing at the time. ... Read more

  Introduction I'm a person that you don't necessarily know, but you may be familiar with some of my work: I act as a Cisco subject matter expert (SME) developing questions for various Cisco exams. My intention here is to describe what it is like to act as a SME so that you may decide whether it is something for you. My experience may not be the exact same as what you (the reader) would ... Read more

IntroductionMost of us have been several times in that place where we - as network engineers - contemplate a network diagram and have several questions come to us like lightning strikes: “Is this the best way to do it?” “Could it be improved somehow?” “What if?” In this write-up I intend to give an introductory view of network design and share situations and ... Read more


Anatomy of GRE Tunnels

Posted by sarah Mar 14, 2017

Introduction With the recent iterations of the CCNA exam blueprint, GRE tunnels have become one of the most commonly discussed topics here on CLN. With this blog, I hope to explain and demonstrate the basic configuration required to form GRE tunnels with specific use cases in mind. I will also address certain pitfalls encountered while implementing GRE tunnels, beginning with a basic overview ... Read more


DMVPN: The Phases In-Depth

Posted by Dmcneil Feb 15, 2017

IntroductionIn this blog, I aim to go a little deeper into how the different DMVPN phases work and how to properly configure the routing protocol to operate in each phase. The routing protocol of choice for this blog is EIGRP classic configuration.   At the end of this blog, the reader should have a solid understanding and justification for each configuration command used in the different ... Read more


Planes and Perspectives

Posted by arteq Jan 17, 2017

For the beginner, embarking on the study of networking can be daunting as it often presents words and concepts once understood suddenly imbued with new meaning. Computer science is a relatively new idea first proposed in 1956 by Louis Fein in a study for Stanford University. The administrators were dubious of what Fein called "computer-related science." A Computer Science Department would ... Read more

SRTP (Secure Real-Time protocol), as the name suggests, is a secure RTP, or in simple terms, encrypted RTP. SRTP can be implemented in both CUCM or CME environments. There are a lot of things involved which we need to prepare before going forward. The goal of this post is to provide an understanding of implementing this protocol, but it cannot be considered as a complete guide because there is so ... Read more

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