Is IPV6 Dual-Stack really a best method for IPv6 design ?

There are mainly three IPv6 transition methods; Dual-Stack, Tunnelling and Translation. Careful engineers can understand the difference between IPv6 migration and IPv6 transition. All of these three technologies are used to bring IPv6 protocol capabilities in addition to IPv4, they are not migration mechanisms. Migration means removing IPv4 completely and running only IPv6 only in […]

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EIGRP RFC 7868

Finally, informational EIGRP RFC 7868 has been published.It is not anymore Cisco’s EIGRP, it is an open standard. Without a most critical feature of EIGRP,can we really say that? Why Cisco doesn’t share the most important feature which can help in large scale EIGRP design although industry has been asking from them for a long time ? […]

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BGP Best External

BGP Best External is used in Active Standby BGP Topologies. BGP Best External helps for BGP convergence by sending external BGP prefixes which wouldn’t normally be sent if they are not overall BGP best path. There are BGP best internal, BGP best external and BGP Overall best path. BGP Best external in an active-standby scenarios […]

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Which company has the most CCDE in the World ?

Which company has the most Cisco CCDE certified engineers in the world? Of course, Cisco  has the most certified engineers across the globe. In this post, I will introduce you to the second company that has the most CCDE engineers in the world outside of Cisco.   I like sharing the Global CCDE List whenever someone […]

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Why Are Dynamic Routing Protocols Used?

Why are dynamic routing protocols used is usually asked by newbies in the networking field, especially after they have heard about routing protocols. Besides that, they often asked this question: What is the difference between static routing and the dynamic routing protocols? And the common answer is that dynamic routing protocols are scalable. In other words, […]

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What is MP-BGP – Multiprotocol BGP

MP-BGP (Multiprotocol BGP) is an extensions to BGP protocol. Standard BGP only supports IPv4 unicast address family, whereas MP-BGP supports more than 15 different BGP address families. RFC4760 defines the extensions for BGP protocol and states that ” in order to bring extra functionality to BGP protocol, new BGP AFI (Address Family Identifier) and BGP SAFI […]

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BGP Next-Hop Behaviour in IP and MPLS Networks

One of my CCDE bootcamp students asked a question about next hop in MPLS VPN network. So, I would be very pleased to explain the BGP next hop behaviour both in IP and MPLS network in this post. Let’s start with this IP network shown below (Figure-1). Figure-1 IBGP Next Hop handling in IP networks In […]

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EIGRP Feasible Successor

One of the advantages of EIGRP Feasible Successor is that it speeds up the EIGRP. In fact, if there is a Feasible Successor in the EIGRP network, such network converges faster than OSPF or IS-IS. But what is EIGRP Feasible Successor and how can we find EIGRP Feasible Successor? Or, if there is EIGRP Feasible […]

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PIM Sparse Mode Vs PIM SSM

One of my students asked me this question a month ago. “What is the difference between PIM Sparse Mode and PIM SSM (Source Specific Multicast)?” But, since I had two CCDE bootcamps in one month, I didn’t have time to answer the question on this platform. By the way I have seen this mis understanding […]

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What is VLAN Load Balancing?

In layer 2 switching, the Ethernet frames should be received from the same port where it was sent, otherwise layer 2 switching or switching loop occurs. Let me explain this concept with the topology depicted below (Figure -1). . Figure -1 VLAN load balancing In the above figure, either Port 1 or Port2 is used […]

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What is DFZ (Default Free Zone)?

In the context of the Internet and BGP routing, DFZ – commonly known as Default Free Zone – refers to the collections of all the public IPv4 BGP prefixes without default route on the global Internet. Most of the time, you hear full-route or full-Internet-route terms which are the same with Default Free Zone term. Having all BGP routes, […]

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Great Cisco CCDE Achievement

Congratulations, Martin J Duggan, for being among one of the two people who passed the May 2016 CCDE Practical Exam. Your hard work has truly paid off not only because you attended my class, but, also because you put in your efforts to make this dream of yours a reality. You have made us proud. […]

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BGP PIC EDGE

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Beware: CCIE University Steals and Cheats

With more than 13 years of IT related experience, I have spent my past few years using my passion in IT to teach Cisco network design concepts such as CCDE, CCDP and CCDA to help Cisco exam takers get successfully certified. Through my work, https://orhanergun.net/ not only became one of the most recognized and well […]

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MPLS Design Question

MPLS Design Question – MPLS is one of the most commonly used encapsulation method today. Especially on Wide Area Networks of the Service Providers, Large Enterprises and some datacenters. Service Providers sell MPLS services to customers for decades. When customers want to have Service Provider redundancy so two MPLS circuit from different Service Providers, Inter AS […]

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What does BGP free core mean ?

What is the meaning of BGP free core? BGP refers to an Internet protocol used between different Autonomous System on the Internet. The purpose of this post is not to explain the fundamentals of BGP, as I believe that readers are already familiar with the basic of BGP and IP routing operation. To understand the […]

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What is RSVP-TE ?

What is RSVP-TE (RSVP Traffic Engineering)?  RSVP-TE refers to a resource reservation protocol that is invented in order to allocate a bandwidth for the individual flows on the network devices. To say it another way, RSVP-TE are extensions to the RSVP protocol specified in the RFC 3209. Although, RSVP-TE has been initially invented as a Quality […]

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HSRP VRRP GLBP Comparison

HSRP VRRP GLBP Comparison– In this post I am going to cover the similarities and the differences between HSRP VRRP and GLBP protocols. All these technologies provide first hop redundancy for the hosts. I will use the below table for HSRP VRRP GLBP Comparison and the design attributes listed in it. For the more technology comparison tables; please click […]

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CCDE Practical Lab Scenarios Bootcamp

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DMVPN vs. GETVPN

DMVPN vs. GETVPN – In this post I am going to cover the similarities and the differences between GETVPN and the DMVPN. For the DMVPN basics, please read this post. Both technologies provide overlay virtual private network in general and I will use the below comparison table and the design attributes listed in it. For the […]

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