OSPF vs. EIGRP Design

This comparison chart and all the knowledge in the article is your ultimate resource for the OSPF and EIGRP routing protocols from the design point of view. Knowing and understanding these design practices will not only help you for the real life network design but also will help for the any design certification exams.

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MANET: Mobile Ad Hoc Networks

The MANET stands for mobile ad hoc network; in practice, the term generally applies to ad hoc wireless networks of sufficient complexity that some internal routing mechanism is needed to enable full connectivity. The term mesh network is also used for MANETs. MANET nodes communicate by radio signals with a finite range, as in the Figure – […]

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What is routing loop, How is routing loop prevented ?

What is a Routing Loop – A potential problem to packet forwarding is the possibility of a routing loop.

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IS-IS Design: Avoiding Traffic Blackholing

IS-IS, a link state routing protocol, requires careful attention during network design in order to avoid traffic blackholing. In the topology below, IS-IS routing protocol is used.

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Datacenter Design: Shortest Path Bridging

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.

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Dual Carrier MPLS VPN Design

For the purpose of high availability, critical locations of company A – a customer of VPN service provider – is connected to two different carriers. However, this connectivity requires an important design consideration.

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OSPF in a Full-Mesh Topology Design

Flooding in full-mesh topology is a big concern for network-design experts, especially in large-scale OSPF deployments. When the link or node fails in an OSPF network, failure information is flooded everywhere in the same area. If Flat OSPF network design is used, then the problem gets bigger. Each router receives at least one copy of the new information from […]

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orhanergun.net 2015 review

As the owner of the best computer network design blog, I am really proud of myself. I am now getting positive feedbacks from users all over the world. In recent times, I have observed that everybody has been reading this blog. Because of this, I owe all the readers of this blog my achievements. Indeed, your […]

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EIGRP Hub and Spoke Design

EIGRP is the best protocol in Hub and Spoke topologies because of many reasons. In this article, I will explain the design consideration for EIGRP in a Hub and Spoke topology, also known as star topologies.

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Single Vs. Dual Carrier Design

Companies don’t always have high availability. What’s more, there is always a concern of budget and complexity with the high availability even though a number of factors need to be considered during network design.

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IGP LDP Synchronization

I implore all my readers to always remember this topic: IGP LDP synchronization. It is important to use IGP LDP synchronization to avoid blackholing, especially when MPLS networks fails to function effectively.     In the topology above, IS-IS is running in the network of the service provider. For the transport label distribution or topmost label/tunnel label, […]

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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 […]

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What is a micro loop in routing?

Micro loop can be found in fast-rerouted networks. Fast reroute, as a proactive convergence mechanism, provides sub-second data plane convergence. If there are technical glitches, upstream node sends the traffic through the repaired path to the downstream device. For the downstream node to be used as a backup/repair node, it should be loop-free. What do […]

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Cisco Press 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 […]

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2016 January Online CCDE Bootcamp

Due to the high level of demand for my early CCDE bootcamps, the increase of individuals pursuing the CCDE and very high passing rate of my class (75%) I have [...]

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HSRP – VRRP – GLBP

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.

source: Orhan Ergun CCDE Study Guide – Workbook

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, lets look at the below picture.

source: Orhan Ergun CCDE Study Guide – Workbook

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 PC we would see different gateway Continue reading