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VIP Perspectives

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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

Recently I have started learning Python. Is it because the sky is falling? Have I handed my CCIE and CCDE plaque back to Chuck Robbins? Not yet…   People that know me know that I have a big hunger for learning things. I’ve been on the networking side for 10 years now, and I decided that I wanted to learn coding to be able to interact better with developers and system ... Read more

The networking industry is a constantly evolving field that needs more and more talented people to start filling roles that are opening up. Even with this, it seems that without experience, it is still hard to break into the industry. This poses a very unique situation out there for people just starting their careers, but there are ways that, with some outside-the-box thinking, breaking into the ... Read more

Cisco Live US 2016 is in the books, and what a great event it was! Like every year, it’s a crazy intense week, and my week was filled with attending sessions, meeting people, doing interviews, and a lot more. I was happy to see a big gathering of both people from Cisco and Cisco VIP’s this year. From the Cisco side, I got to meet Karlo Bobiles for the first time. Matt and Brett were ... Read more

DMVPN Overview  Dynamic Multipoint Virtual Private Network (DMVPN) is a cost-efficient, scalable technology used to connect multiple sites together. DMVPN is a solution that comprises three main technologies: Multipoint GRE tunnels NHRP IPsec.   I will not focus on DMVPN configuration but rather on how Multipoint GRE tunnels and NHRP rely on the next-hop value in the routing table to ... Read more

What is “virtual” – not reality?   This idea could launch a philosophical discussion. It harkens back to Rene Descartes proving his very being with the proclamation: "I think, therefore I exist" (“Cogito, ergo sum”) and laying the groundwork for further proof of the surrounding material world and the necessary connectivity of "things" (or metaphysics).   ... Read more

Introduction In today’s networks, it is almost impossible to find a network professional who has never been in touch with fiber-based links between switches, routers, or other network devices. The widespread use of fibers makes a lot of sense, since a single strand of fiber can provide very high capacity.   Some of the first commercial fiber links were deployed in the mid-1970’s ... Read more

Hi guys,   I hope you all are well. In this blog, I would like to share with you a real world scenario I came across last week from a customer who had the following requirements:   Users have to connect to the LAN through AnyConnect SSL VPN on a non-default port; AnyConnect users have to authenticate through the existent Active Directory/LDAP server in the LAN; AnyConnect clients have ... Read more

Advanced STP features is perhaps one of the most commonly misunderstood topics in any Cisco certification level studies. From what I have found, the features are somewhat unclearly documented and some information available out there is even plain wrong. This post describes the operation of PortFast, BPDU guard, and BPDU filter in detail.   PortFast  The PortFast feature was originally ... Read more

Elvin Arias

Why Telnet Is Bad

Posted by Elvin Arias Feb 19, 2016

Remote network connection is critical for managing the enterprise network devices. Accessing the routers and switches is vital for the network administrators in order to execute daily operational tasks, which include (but are not limited to): Creating and removing VLANs. Adding and removing interfaces. Shutting down or enabling interfaces. Routing configuration, e.g. adding or removing static ... Read more

Hi all, This is my first blog, I hope readers will find of value in it. I’m going to be concise and focus on the topic without overwhelming you with lots of explanations, hopefully it will light and welcoming to read.   Today I’m going to talk about NAT exemption. As we know NAT plays a very important role in our networks today. And there are different of types and a bunch of ... Read more

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