What is Urban and Rural area in networking ?
What is urban and rural area ? What is underserved area in networking ?
These definitions are heavily used in networking. And all broadband network designers take always these definitions into an account while they do their design. I think knowing these definitions as a network engineer is valuable for you.
In general, a rural area or countryside is a geographic area that is located outside towns and cities
Whatever is not urban is considered rural area though some people uses less populate than urban but more populated than rural area as suburban area
Typical urban areas have a high population and large settlements
Typical rural areas have a low population density and small settlements
Underserved areas where there is no good network coverage (Broadband , Voice or any other data types)
Unserved areas where there is no network coverage at all
For example,if mobile operator will place a cell sites in an urban area, since the population density will be too high, they consider to place more cell sites than if they place those cell sites in a rural area.
FTTx planers consider to change their ODN (Optical Distribution Network) design entirely depends on they are doing FTTx deployment in Continue reading
Congratulations to Roy Lexmond on Passing CCDE Practical Exam!
I am very glad to announce that Roy Lexmond from my April CCDE training class passed CCDE Practical exam yesterday in France.
Below is his success story and here is his earlier feedback for the class. I should say that He really likes the design and open to learn new things and very clever.
Please join me to congratulate Roy for his great achievement!
On 19th May in France (Paris) I passed CCDE practical exam. My preparation was done with the cisco learning network excelsheet, Ciscolive video’s, internetworkexpert SP&CCDE courses, Orhan Ergun CCDE Bootcamp and www.orhanergun.net. I attended the Orhan Ergun bootcamp in April-May with lots of great people which helped me prepare well. I really think that the bootcamp helped me to focus on key technologies and discuss them with other people (very important for me) and to understand how to approach the exam.
It was a challenge and took me 2 years, my satisfaction is extreme! and learned alot during those 2 years and still learning. My next goal will be CCIE-SP wich covers some great content inline with the topics the CCDE already covered.
Roy Lexmond
Senior Network Engineer at Routz
CCIE#26557/CCDP/CCDE
I promise to Continue reading
Flat/Single Area OSPF network is not a problem!
Flat OSPF network, or single area OSPF networks are real. In fact most of the OSPF network today deployed, is flat OSPF networks. But how many routers can be placed safely in an OSPF area ? Any number from the real world OSPF deployment ? I will share in this post.
Let me explain what it is first and then will share you some numbers from the real network which I engaged recently.
As you might know, OSPF has two levels of hierarchy. Backbone and Non-Backbone areas.
Why Non-Backbone Areas are used in OSPF?
The reason is scalability and manageability. At least in theory. I don’t see so many multi area OSPF design though I teach in very detail in my CCDE classes. But that is for the exam purpose.
There are some very large scale networks use OSPF for scalability, so, IP but satellite (Sometimes called an Access POP) POPs are in Non-Backbone area they place.
But there is manageability aspects of having multi area OSPF design. They group their slow speed access and metro or aggregation networks in different OSPF areas and place high speed backbone/core routers in a backbone OSPF area (Area 0).
But, we generally forget Continue reading
CCDE Study Guide
CCDE Study Guide – Are you looking for a book that will teach you all the topics on advanced technical networking? If so, I would be very pleased to recommend CCDE Study Guide written by Marwan Al-Shawi to you.
As one of the professionals who contributed immensely to this book, I must admit that Marwan wrote this book in collaboration with a number of savvy designers. IT experts who contributed to this wonderful book include Russ White, Andre Laurent, Denise Fishbourne, Ivan Papeljnak, and Orhan Ergun. In fact, all the IT concepts in this book are enlightening! The book has many drawings, which will assist learners to understand network design.
Today, I spoke with one of my old friend, an expert in CCDE, who read Marwan’s book, and his comment was this: “The book contains pictures that explain a thousand words.”
The most important topics of the networking design, especially for the CCDE exam, are layer 3 technologies such as IGP, BGP, MPLS, Inter-AS MPLS, and IPv6 and VPNs. These topics are extensively covered in this book.
These topics are very important because CCDE exam is a layer 3 infrastructure exam and because these technologies provide an Continue reading
Recommended Networking Resources for September 2019 First Week
I would like to share with you every week some networking resources , can be video , article , book , diagram , another website etc.
Whatever I believe can be useful for the computer network engineers, mobile network providers, satellite engineers ,transmission experts, datacenter engineers, basically whatever I am interested in and I like, I will share in a blog post.
There will not be any order of importance among the resources. You can open and go through anyone you want.
I will try to limit the list with 5 resources as I want you to read the posts that I publish on the website. Sometimes can be more than 5 though!
Let’s get started!
TCP vs QUIC – Quic is a new transport protocol I think everyone should have a look at. What are the high level differences between them etc.
TCP vs QUIC: A New Transport Protocol
2. Below post explains how BGP As-Path prepending , when it is done more than couple times , can be dangerous for the attacks on BGP information security
Excessive BGP AS-PATH prepending is a self-inflicted vulnerability
3. This presentation is one of the best presentation about BGP Continue reading
Interdatacenter broadcast control – ARP Proxy in OTV and EVPN
When it comes to multi domain or Inter datacenter communication, minimizing the broadcast traffic between the datacenters is an important scaling requirement.
Especially if you are dealing with millions of end hosts, localizing the broadcast traffic is critical to save resources on the network and the end hosts. Resources are bandwidth , CPU , memory and so on.
In this post I will mention how ARP cache is populated in OTV and EVPN technologies and the importance of ARP proxy function.
Classical approach to control broadcast traffic by localizing it within a datacenter is Proxying.
ARP is a good example of broadcast packet and ARP Proxy or Proxy ARP works either based on control or data plane learning.
Idea is, destination MAC address can be learned from the local device which keeps ARP cache and ARP traffic doesn’t have to traffic over datacenter interconnect links.
I said ARP cache can be populated either via control or data plane learning and let me give an example for each one of them.
OTV as a Cisco preparatory protocol advertise the MAC addresses through IS-IS. MAC reachability information is learned via control plane. But OTV doesn’t advertise MAC to IP binding through IS-IS. Continue reading
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?
- If there is EIGRP Feasible Successor, how does EIGRP converges faster than OSPF or ISIS?
In this post, I will explain the answers to the above questions.
EIGRP Feasible Successor is a backup node that can satisfy the EIGRP feasibility condition.
Feasibility condition simply means that the backup router should be loop-free.
Let’s examine the topology shown below (Figure-1) to understand how EIGRP finds loop-free alternate/backup node.
Figure-1 EIGRP Feasibility Condition
From the Router A’s point of view, Router B and Router C are the equal cost routers; as a result, both ABD and ACD path can be used in the network. What’s more, Router A installs both Router B and Router C not only in the EIGRP topology table but also in the routing table.
There is no backup router in the above topology since Router A uses both Router B and Router C to reach the destination Continue reading
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 ?
EIGRP RFC 7868 specifies EIGRP Dual Algorithm, EIGRP Packets such as Update, Query and Reply, EIGRP Operation, and EIGRP Metrics (K1,K2,….K6).
And since EIGP is RFC anymore, other vendors can legally implement EIGRP. There was couple of open source EIGRP implementations already,but with the RFC status, seeing new implementations among the big vendors would not be a big deal.
In addition to EIGRP packet types and metric values, there are a couple of important things to understand about EIGRP.
Among them is how EIGRP, as a distance vector protocol, calculates a best path and advertise it to the neighbors.
Understanding what is EIGRP successor, EIGRP feasible successor, EIGRP feasibility condition, metric values and usage in real life deployments is among the most important parameters in EIGRP that should be properly understood.
EIGRP RFC is an 80-page document, which provides detailed Continue reading
BGP Best External Feature
BGP Best External is used in Active Standby BGP Topologies generally but not limited with that.BGP Best External feature helps BGP to converge much faster by sending external BGP prefixes which wouldn’t normally be sent if they are not overall BGP best path.
I am explaining this topic in great detail in my Live/Webex “BGP Zero to Hero” course.
There are BGP best internal, BGP best external and BGP Overall best path.
BGP Best external in an active-standby scenarios can be used in MPLS VPN, Internet Business Customers, EBGP Peering Scenarios, Hierarchical large scale Service Provider backbone and many others.
But,How active-standby scenario connection with BGP is created ? In which situation people use active-standby instead of active-active connection ?
Let’s start with the below scenario.
Figure -1 BGP Active-Standby Path Selection Example
First thing you should know that common reason for active-standby or primary-backup link is one link is more expensive than the other.Cost doesn’t have to be a $$ cost only but also be based on latency, performance and bandwidth.
In Figure-1 : IBGP is running in the Service Provider network. Between R1 , R2 and R3 there is an IBGP Continue reading
DMVPN Point-to-Point GRE and mGRE
DMVPN spokes can use either point-to-point GRE tunnels or multipoint GRE tunnel interface. Recently, I received a question regarding DMVPN.
In fact, the Reader asked me two questions: When is GRE used in network design? When is mGRE used in network design?
Answering the aforementioned questions are the basics that you must know if you are planning to design DMVPN network.
As you might have known, DMVPN is a hub, spoke type of topology. And the most useful, important functionality of DMVPN is that it provides excellent scalability by reducing the number of tunnel interfaces configured on the hub and spokes.
I mentioned the DMVPN phases in one of my articles. Because of that, I will not explain them here again. However, if you don’t understand the meaning of DMVPN phases, I would recommend that you peruse the article on DMVPN basics before reading this article.
Point-to-Point GRE interface is used, only in Phase 1, on the spokes.
In all the Phases, mGRE interface type is always used on the hubs.
In Phase 2 and Phase 3 of DMVPN implementation, spokes also use mGRE (not multicast GRE, but multipoint GRE) interface types.
Compared to the point-to-point GRE interface, mGRE provides Continue reading
2017 CCDE Exam Dates!
2017 CCDE Exam dates has been announced.There are four CCDE exam every year. More precisely there are four CCDE Practical/Lab exam every year. There is no limitation for the CCDE Written exam.
You can join CCDE Written exam anytime in any Pearson Vue Center. It is not only 4 times in a year.
CCDE Practical exam is not only in the Cisco Office anymore, but it is in the Professional Pearson Vue Locations. There are 275 of them and unfortunatelly, not every country has PPC (Professional PearsonVue Center)
If you are in Middle East, India, Turkey, Greece and Europe would be nice location.
I attended and passed the exam in Greece and Athens is one of the most beautiful city guys 
I definitely recommend it.
Below is the 2017 CCDE Practical/Lab exam dates and I wish Good Luck for everyone and definitely recommend my Self Paced CCDE Training or Instructor Led CCDE Training.
Nothing Should Stop You!
As many of you know, I was born in Turkey. And unfortunately, the educational system of that country is very weak. And guess what: If you can’t afford to go to private school in Turkey, you may not be able to learn English in the government school.
However, if you are a very diligent student, you may learn the basics of writing or speaking English. I have decided not to allow my proofreader to edit this post. My reason is simple. I want you to notice that I am still struggling with English. But that’s okay. It’s a learning curve. So, nothing should stop you !|
My aim of writing this post is to share some of my thoughts with you. And I know many people will read this and I hope it will inspire some of you.
I worked as a network operation center engineer, presales engineer and consultant while I was in Turkey. Fortunately, I joined and managed many design projects during that time. After that, I moved to other countries with the aim of sharing my knowledge with others and getting some money of course
At this point, you might be having this thought: “With your weak Continue reading
Is Cisco CCDE Exam Vendor Neutral?
Is Cisco CCDE Exam really vendor neutral?.Recently one of my CCDE Bootcamp students asked me this question. He heard that DMVPN might come in the exam.
In the beginning of my each CCDE class, I introduce the topics which will most likely asked in the CCDE Practical exam. Cisco claims that CCDE Practical exam is vendor neutral network design exam.
And I totally agree. Actually not only DMVPN, but also HSRP, GLBP, EIGRP, GETVPN might come in the exam and you should know the details of these technologies from the design point of view.
All these technologies are Cisco specific, why then it is vendor neutral ?
Reason is simple but not maybe obvious for those who don’t know the details of the exam.
These are very commonly deployed technologies in the networks. Almost everyone learned HSRP when they studied first hop redundancy protocols, I believe, right ?
Or, can be any decent network engineer who don’t know EIGRP ?
If you think that you know routing protocols, or you think that you are familiar with them, you have to know it.
But it is not about that they are commonly used technologies.
They are actually derived from the very well known Continue reading
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.
To have a great understanding of SP Networks, you can check my new published “Service Provider Networks Design and Architecture Perspective” Book.
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)
NFV offers a way to design, deploy, & manage Network Services via decoupling the Network Functions from proprietary Hardware enabling them to run in Continue reading
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.
To have a great understanding of SP Networks, you can check my new published “Service Provider Networks Design and Architecture Perspective” Book.
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 Continue reading
Common Networking Protocols in LAN, WAN and Datacenter
Spanning Tree, Link Aggregation , VLAN and First Hop Redundancy protocols are used in Campus, Service Provider Access and Aggregation and in the Datacenter environment. There are definitely other protocols which are common across the Places in the Networks but in order to keep this article short and meaningful I choose these four.
I will describe Spanning tree, link aggregation, 802.1q Vlan and First hop redundancy protocols at a high level since I will explained them in detail later in the separate articles.
For the more advanced layer 2 protocol information check this article.
Spanning Tree – IEEE 802.1d, 802.1w, 802.1s
Spanning tree is used to build a control path between the Ethernet switches in the campus , service provider and data center environment. It prevents data plane loops by creating a tree !
Loop preventation is very crirical for the Ethernet since there is no TTL value or any other loop mitigation mechanism encoded in the Ethernet header.
Loop prevention is achieved by blocking the link which has a higher cost to the root switch in the topology.
802.1d is also known as original spanning tree or legacy spanning tree has been Continue reading
Push and Pull Based Control Plane Mechanisms
Control plane packets are used to build a communication path between the networking devices. In some cases control plane is used to advertise and learn the endpoints.
Imagine a network which consist of these networking devices, in order to crate a graph or tree among them for bridging or routing purpose, control plane protocols are used.
As a network engineer although I keep Application requirements in my mind during a network design, in general layer 4 and above is just boring.
Spanning tree, G.8032, RPR, Trill, SPB, Fabricpath,EAPS, PBB-TE (PBT) are the control plane protocols at the layer 2. They are used to create a communication path , in general a tree. Some of them allow Vlan based load balancing , some of them allow flow based load balancing with ECMP ( Equal Cost Multipath ) or ECT ( Equal Cost Tree ).
But if you read so far, I didn’t mention from reachability information. For the layer 2, reachability for us, Ethernet Mac addresses, Frame relay pdu, ATM cells etc, all of the above protocols are used for Ethernet control plane though.
In general ( SPBM is different ), reachability information is learned through flooding and learning Continue reading
Datacenter Design: Shortest Path Bridging 802.1aq
IEEE 802.1aq Shortest Path Bridging (SPB) uses IS-IS as an underlying control plane mechanism that allows all the links in the topology to be active.
In sum, it supports layer 2 multipath. SPB is used in the datacenter; however, it can also be used in the local area network. In this article, Figure-1 will be used to explain shortest path bridging operation.
Figure-1 – Leaf and Spine Topology
In Figure-1, both leaf and spine nodes run IS-IS to advertise the topological information to each other.
In SPB, IS-IS is used by the bridges to find the shortest path to each other, and it allows the topology to be calculated.
But unlike routing, large scale bridging uses only IS-IS link state protocol for the topological information, not for the reachability information.
This means that the addresses of MAC are not advertised within IS-IS.
Some vendor implementations can also use IS-IS to advertise MAC address information since they only need an additional TLV for this operation. Scalability of IS-IS for the MAC addresses advertisement is questionable for large scale deployment; thus, both BGP for MAC address distribution and IS-IS for physical topology creation might be a good option.
HSRP, VRRP and GLBP Basics and Comparison
HSRP, VRRP and GLBP are the three commonly used first hop redundancy protocols in local area networks and the data center.
In this post, I will briefly describe them and highlight the major differences. I will ask you a design question so we will discuss in the comment section below.
I am explaining this topic in deep detail in my Instructor Led CCDE and Self Paced CCDE course.
HSRP and GLBP are the Cisco specific protocols but VRRP is an IETF standard. So if the business requirement states that more than one vendor will be used , then VRRP is the best choice to avoid any vendor interoperability issue.
For the default gateway functionality HSRP and VRRP uses one virtual IP corresponds one Virtual Mac address.
GLBP operates in a different way. Clients still use one virtual IP address but more than one virtual mac address is used. So each default gateway switch has its own virtual Mac address but same virtual IP address.
To illustrate this, let’s look at the below picture.
In the above picture, clients use same gateway mac address since the first hop redundancy protocol is HSRP.
If GLBP was in used, on the Continue reading
Inter AS Option C – Design Considerations and Comparison
Inter AS Option C is the most complex, insecure, uncommon, but extremely scalable inter provider MPLS VPN solution.
I am explaining this topic in deep detail in my Instructor Led CCDE and Self Paced CCDE course.
In this post, I will explain how service providers can use Inter AS Option C to assist customers to have an end-to-end MPLS VPN service.
In the Inter AS Option B post, I explained that ASBR routers between the service providers do not keep a VRF table for the VPN customers.
As depicted in the fig.1 (shown below), as for Inter AS Option B, MP-BGP VPNv4 session is set up between service providers’ ASBR PEs.
Figure 1: Inter-AS Option B
As for Inter AS Option B, ASBR routers – the provider-edge devices between the service providers – maintain only the VPN prefixes of the customers in the BGP table.
In fact, I have shown that VPNv4 BGP session has been set up between the ASBRs.
The high-level operational differences between Inter AS Option C and Inter AS Option B are in two folds: one is that ASBRs do not have VRF table; the other is that unlike Continue reading