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Benefits of MPLS – Why MPLS is used ? – MPLS Advantages

Benefits of MPLS, Why MPLS is used on today networks and the Advantages of MPLS will be explained in this post.

As an Encapsulation and VPN mechanism, MPLS brings many benefits to the IP networks. In this article most of them will be explained and design examples will be shared by referring more detailed articles on the website as well.

Below list shows the benefits of MPLS. Although this may not be the full list, comment section always open for your comment and questions.


  • Faster packet processing with MPLS compare to IP

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Orhan Ergun No Comments

BGP in MPLS Layer 3 VPN – BGP as a PE-CE Routing Protocol

BGP can be used as a PE-CE routing protocol in MPLS Layer 3 VPN. Also Service Providers run MP-BGP (Multiprotocol BGP) if they have MPLS Layer 3 VPN.

In this article, MP-BGP will not be explained since it has been explained here earlier in detail.

When BGP is used as a PE-CE routing protocol between the customer and its MPLS Layer 3 VPN Provider, it is important to say that there is no need to redistribute on the Service Provider PE. All the other routing protocol require redistribution from MP-BGP into the routing protocol and vice versa.

In this post, I will explained what are the design considerations when BGP is used as PE-CE routing protocol in MPLS Layer 3 VPN and the how you can mitigate possible routing loop problems.

Last but not least, I will share when CE (Customer Equipment) is multihomed to two PEs (Provider Edge Device), what would be the design considerations if BGP is used in MPLS Layer VPN. Read more

Orhan Ergun No Comments

OSPF to IS-IS Migration

There are many reasons of OSPF to IS-IS migration, specifically for the Service Provider networks. Some of these reasons are shared later in the case study.

OSPF to IS-IS migration can be done in three ways. Read more

Orhan Ergun No Comments

Design considerations for network mergers and acquisitions

Network mergers and acquisitions are the processes which can be seen in any type of businesses. As a network designers, our job to identify the business requirements of both existing networks and the merged network and finding best possible technical solutions for the business.

There are many different areas which need to be analyzed carefully. Wrong business requirement gathering and design analyze, definitely lead to catastrophic failures.

Business and network analysis and technical information gathering are the key steps and there are many questions which need to be asked and answered should be well understood.

Network mergers and acquisitions is also called as Network integration.

Below are the key points for any type of network mergers and acquisitions projects.

  • Business analysis and information gathering

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Orhan Ergun No Comments

OSPF Multi-Area Adjacency | OSPF Area Placement | RFC 5185

OSPFv2 by default setup only one adjacency over a single link. But this can be an issue some time and as a network designer you should understand the consequences and know the available solutions.

Placing a link in wrong OSPF area can create an OSPF sub optimal routing especially in hub and spoke topology.

In IS-IS or OSPFv3, this wouldn’t be an issue because IS-IS and OSPFv3 allow link to be placed in more than area or level. (In IS-IS, area is assigned to the router, not to the link. Thus I use level keyword)

Let’s look at the below network to understand what is the issue and how OSPF multi-area adjacency can solve the sub optimal routing problem. Read more

Orhan Ergun No Comments

IS-IS Design considerations on MPLS backbone

IS-IS Design considerations on MPLS backbone

Using IS-IS with MPLS require some important design considerations. IS-IS as a scalable link state routing protocol has been used in the Service Provider networks for decades.

In fact, eight of the largest nine Service Providers use IS-IS routing protocol on their network as of today. Read more

Orhan Ergun No Comments

Carrier Ethernet – Definition | Service Types | Requirements


Carrier Ethernet is an attempt to expand Ethernet beyond the borders of Local Area Network (LAN), into the Wide Area Networks (WAN).

With Carrier Ethernet, customer sites are connected through the Wide Area Network. Carriers have connected the customers with ATM (Asynchronous Transfer Mode) and Frame Relay interfaces in the past. (User to Network Interface/UNI). Read more

Orhan Ergun No Comments

IPv6 Transition Mechanisms | Dual-Stack -Tunneling – Translation

IPv6 Transition Mechanisms

The only available public IP addresses are IPv6 addresses. But vast majority of the content is still working on IPv4.

How IPv6 users can connect to the IPv4 world and How IPv4 users can reach to the IPv6 content ? This is accomplished with the IPv6 transition mechanisms.

In this post, I will explain the IPv6 transition mechanisms briefly, share some of my IPv6 real life design experiences and observations and will provide a road map for the future IPv6 design and deployment resources which I am going to cover on the website.

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Orhan Ergun No Comments

BGP Peering – Private, Public, Bilateral and Multilateral Peering

BGP Peering

BGP Peering is an agreement between different Service Providers. It is an EBGP neighborship between different Service Providers to send BGP traffic between them without paying upstream Service Provider.


To understand BGP peering, first we must understand how networks are connected to each other on the Internet. The Internet is a collection of many individual networks, which interconnect with each other under the common goal of ensuring global reachability between any two points.


BGP peering
BGP Peering and Transit Links

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What is reliability in networking ?

What is reliability in networking ? Why reliability is an important design tool ? I will provide the answers of these questions with the examples in this post.

Reliability is within the reasonable amount of time, which depends on the application type and architecture, delivering the legitimate packets from source to destination.

This time is known as delay or latency and it is one of the packet delivery parameters. Consistency of delay known as jitter and it is very important for some type of applications such as voice and video, jitter is our second delivery parameters.

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Spanning Tree Best Practices

Spanning Tree Protocol (STP) is a control plane mechanism for Ethernet. It is used to create a Layer 2 topology (a tree) by placing the root switch on top of the tree.

Since classical Ethernet works based on data plane learning and Ethernet frames don’t have TTL for loop prevention, loops are prevented by the STP blocking the links.

As you can see from the below figure, some links are blocked by the spanning tree. If Spanning Tree wouldn’t block those links, loop would occur in the below topology.

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Orhan Ergun 1 Comment

BGP (Border Gateway Protocol) Quiz,Questions and Detailed Answers

BGP (Border Gateway Protocol) a.k.a Bloody Good Protocol quiz !

I prepared 20 Questions in this quiz for you. Intend of this quiz to provide you the BGP design information.

This quiz is part of the BGP Review Questions of my upcoming new version of CCDE Workbook. There will be hundreds of questions in it and will be available shortly !

This quiz helps for CCDE Written and CCDE Practical exam as well as real-life Network Engineering Interviews.

For more quizzes and many other design resources such as videos, mind maps and the my books, you can subscribe and access immediately. Click here to subscribe Self Paced CCDE Course 

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Orhan Ergun No Comments

Four of my students passed the CCDE Practical exam in August 2016

Hi everyone,

I am glad to announce that below 4 of my students passed the CCDE Practical exam in August 2016 after attending my CCDE Training Program and got their CCDE numbers yesterday.

You will have their success story and CCDE exam preparation recommendations on www.orhanergun.net  in couple days. They are still celebrating it 🙂

November 17 is the only CCDE Practical exam date left this year. Join my November 10 days CCDE Training Program.

You can still have your 2016 CCDE number ! Learn More..

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Hashiru Aminu CCDE Exam Success Story and Recommendations

I took the coveted CCDE  Practical Exams on 31st of August, and Thankfully I passed (My CCDE Number is 2016::14), this is my third attempt, the journey started in 2011, Gone through a lot of studies, Boot camps, Ciscolive Sessions, CCDE Mock Lab in Ciscolive, Mentorship from existing CCDEs.

My First attempt was in 2014 that ended with an average score, the second attempt was in February, 2015. The second attempt made me change a lot of my strategies as this beast requires a totally different approach and preparation than CCIE.


My Advice to the CCDE Candidates:

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Orhan Ergun 2 Comments

Inter-AS Option AB (a.k.a Option D)

Inter-AS Option AB is also known as Option D or Hybrid Inter AS Option. It is called Hybrid because Inter-AS Option B uses the best capabilities of Inter-AS Option A and Inter-AS Option B. These capabilities will be explained throughout this post.

MPLS VPN providers often need to inter-connect different ASes to provide VPN services to customers.

Inter-AS Option AB first deployed by Cisco but today many vendors including Juniper provides Inter-AS Option AB feature.

But what are the best capabilities of the Inter-AS Option A and Inter-AS Option B ? Read more

Karim Rabie 1 Comment

Mobile Broadband – Trending Technologies

For me and for most of Mobile broadband professionals, we are used to meeting the Telco Vendors such as Ericsson, Huawei, Cisco, Nokia, etc. It was a mind-shift for me personally when I started to meet RedHat, Mirantis, & Vmware as a part of the NFV talks and I was really surprised that a company like RedHat is a member of the European Telecommunications Standards Institute (ETSI) with more focus on the Mobile Broadband Evolution participating in Mobile Edge Computing (MEC) Work Group.

It is obvious nowadays that the borders between different technology domains are fading in the sense that Networks are shifting into software-defined Networks with new abstraction layers realizing network convergence.

With this post being the last one, I chose to talk a little bit about some trending and future Mobile Broadband technologies with the goal of having an overview of the Technology Roadmap.

NFV (Network Functions Virtualization)

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Orhan Ergun 1 Comment

August 2016 10 days Online CCDE Training

ccde bootcamp orhan ergun



CCDE Bootcamp – This is 10 days  Online Cisco CCDE exam preparation training. No travel, no accommodation or any other extra cost !


Probably you all know the success of Orhan Ergun’s CCDE Bootcamps and how it has been helping so many engineer to become a better network engineer/designer. If you don’t know, please just take a tour on the website. Check the Success Stories/Testimonials. 10s of my students passed the CCDE exam already !

Let’s continue to our journey with the August 2016 CCDE class. 10 days very comprehensive Cisco CCDE course !

Please note that, there is a 20% discount for the registrations until 5th of August.

When you register to this class, any upcoming retake is totally free.

I will place you in a study group with the other 20 CCDE candidates. Even after the class we will continue to study together.

Are you ready to pass the most respectful Cisco certificate !

Register Today with 40% Discount 



Module #1 Introduction to CCDE exam Read more

Karim Rabie No Comments

Evolved Packet Core – Welcome to Long Term Evolution!

As an end user, I am always welcoming the “4G” Signal indicator on my mobile because basically for me this maps to a better Download Speed, good quality VoIP calls (skype, Hangout, Whatsapp, etc) , better Streaming, and HD Videos.

Screen Shot 2016-07-23 at 5.03.16 PM

This article is all about the “4G” indicator. I am discussing the Evolved Packet Core together with the EUTRAN, Evolved Universal Terrestrial Radio Access Network Technologies that are realizing the 4G Service offered to end users.



With Data rates above 100 Mbps and latency of milliseconds that enables the best video streaming and online gaming experience; One may think of 4G networks as a replacement for 2G/3G Network which is valid in some cases. However, we see that the decision to “dismantle” 2G/3G is still in the operators roadmaps.

Before we go through the  LTE/EPC Network Setup, Let’s list three main definitions and abbreviations that are closely related to 4G. Read more

Orhan Ergun No Comments

IS-IS level 1, IS-IS Routing Protocol Levels

What is IS-IS Level 1 ? Why IS-IS level 1 is used ? What are the IS-IS levels ? What is the corresponding Area type in OSPF ?

IS-IS Level 1 is also called as IS-IS Level 1 sub domain. IS-IS is a link state routing protocol, similar to OSPF. You can read detail comparison of OSPF vs. IS-IS from here.

There is an Area concept in IS-IS as well but the purpose of IS-IS Areas are different than OSPF Areas.

In IS-IS Areas are used to create  IS-IS Levels and IS-IS Levels are the similar logical concepts with OSPF Areas.


Two create IS-IS Level 1 adjacency between two routers, same IS-IS area number should be used. Otherwise only IS-IS Level 2 adjacency can be created. This is the first rule of IS-IS adjacency relationship.


Which OSPF Area type is similar to IS-IS Level 1 Sub domain ?

Read more

Orhan Ergun No Comments

What is MPLS tunnel label and why it is used ?

In networking we use many times different terms to define the same thing. MPLS tunnel label or transport label are just two of those.

Not only transport and tunnel labels but also other terms are used to define the same thing which these labels provide.

Let me explain first why and where MPLS tunnel label is used. Read more

Karim Rabie No Comments

PS Core Network Concepts

Most of the educational documents related to PS Core Network start with Call Flows. Attach Call Flow, PDP Context, Paging, etc. Basically that was my problem when I started working in PS Core because the Call Flows include a lot of messages which in turn include a lot of parameters and Information Elements so starting with the Call Flows without knowing at least the Identifiers included in these messages is not the best approach to understand PS Core principles.

This is why this article will be all about the MBB terms that are commonly presented in all Call flows and in most of the MBB talks in general. Once one is comfortable with that, the Call flows will be easy to interpret.

I am bringing some for clarification.

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Karim Rabie No Comments

Core Network Architecture in 3G Mobile Networks

Core Network Architecture in 3G Mobile Networks – Most of the Mobile Broadband Networks worldwide are currently delivering Data Services based on 3G & 4G Technologies. Although 4G/LTE is widely deployed globally but still there are countries and operators running 2G/3G with relatively convenient Data rates to the market demands.

In this article, I am focusing on the Packet Switched Network Architecture in 3G, the corresponding interfaces, & the relevant protocols relying on the terms and principles explained in the first article.

Mobile Broadband Ecosystem

The Basic Core Network Architecture in 3G mobile network is shown in the below figure :

Blank Flowchart - Main PS Core

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Karim Rabie No Comments

Mobile Broadband Ecosystem

Mobile Broadband… You might have heard this term before, possibly in an ISP environment. The term has always represented a name of a department within a mobile operator or a vendor organization. It is always there in profile description for telecom professionals. It is everywhere actually when it comes to a certain ecosystem or framework that delivers Internet Service using Mobile Network.

Let me bring the Wikipedia definition followed with a small note …

Mobile broadband is the marketing term for wireless Internet access through a portable modem, mobile phone, USB wireless modem, tablet or other mobile devices.

Definition is true but the note here is that you can’t rely solely on google to understand the MBB related technologies (EDGE, UMTS, 4G/LTE, etc.) because what is in google is mainly the marketing articles and the vendor specific publications which is fine but as a lesson learned, one need always to understand the technology concept decoupled from vendors influence.

The good thing is that the whole knowledge, principles, & Service descriptions for Mobile Broadband is there in the standards. Mainly the 3GPP which is freely accessible. So I’d clearly say that the “debate” that it is hard to get the knowledge of the MBB is “debatable“!



One just need to know how to get the information? Which 3GPP standard Specifications? Which 3GPP Release? Throughout this article, I am going to talk about the Mobile broadband evolution and the related standardization specifications which will enable the audience to see the big picture of the MBB and the plan is that by the end of the Five articles series, readers will be on the Mobile Broadband Track. Read more

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Is CCDE Practical exam changing in 2016 ?

I read lots of comments on the blogs and forums about CCDE exam changes. People think that CCDE Practical exam is going to change by July 2016.

Guys, be relax. CCDE Practical/Lab exam is not going to change , Cisco will not add any vendor specific SDN technologies into the CCDE Practical exam.

But in July 2016, Datacenter, Automation, SDN topics (Cisco call them emerging technologies) will be added to the exam.

And of course some of the questions will be about Cisco ACI as well. But of course not configuration parameters or low level details of the solution.

I expect more conceptual things which look after why things are done rather than how they are done.

  • Why ACI should be used ?
  • Which environment ACI makes more sense more ?
  • How it can be deployed with the legacy datacenter architecture together ?
  • Why companies would like to have private Cloud and the Private or Public datacenters ?

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