Out of Band Management Networks – Console Servers

Building a robust out of band management network is a critical part of any service provider or large enterprise backbone. Although failures may not occur frequently but believe me if you are not prepared when they happen you will know how OoB management is important and critical. Network failures do happen for reasons ranging from human errors to power or hardware failures. One of your main objectives as a network designer is to keep your network available and achieve the highest possible up-time. There are a lot of things you can do to achieve these objectives in terms of redundancy …

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Cisco Profit up 79% Stock down 8%

Last Wednesday Cisco announced its fourth fiscal quarter financial reports. Cisco reported a 79% jump in profit however its stock price fell down by 8% in after hours trading as sales were slightly below analysts’ expectations. The question is Why this strong negative reaction? Lets take a closer look; the world is being very cautious recently about financial and economic indicators, no one really knows what is going to happen as economic and financial indicators are so confusing and showing mixed signals. Some indicators warn of  the possibility of a double dip recession while others indicate that things is still …

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What you need to know about ADSL (broadband Networks #1)

ADSL !!! I can hear you say “I know everything about ADSL, its a mature technology and I already know it inside out, why is he  writing about ADSL now?” To be honest I am also surprised by writing about ADSL after working with it for about 7 years now and the rest of the world is talking about FTTx technologies.However, I found it a good start for a series of posts about broadband technologies. Although ADSL is a mature technology, it is still growing even after the spread of fiber technologies and I believe it has the potential to …

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The endless story of OSPF vs IS-IS – Part 4 “The Inside Out”

In this post we’ll be covering a couple of topics from the Inside Out of the link-state protocols that have always been ambiguous and full of details, we’ll try to make them as crystal clear as we can. MTU: Both link-state routing protocols consider MTU in order to prevent any related problems, mainly loss of routing information due to large routing messages being dropped (consider an OSPF LSU or an IS-IS LSP that is over sized and thus dropped), however each protocol tests the MTU in a different way as we’ll see in the upcoming section. OSPF requires routers to …

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The endless story of OSPF vs IS-IS – Part 3 “Packets and Database”

In this post we are going to cover the protocol packets and database structure for both routing protocols. To start let’s first highlight a couple of facts. OSPF runs on top of IP, that is it uses IP packets to exchange its messages (and thus it is vulnerable to spoofing and DoS attacks, and accordingly the use of authentication is strongly recommended), while on the other hand IS-IS runs directly over layer 2, it creates its own packet (or PDU (Protocol Data Unit) to be more specific) and then encapsulates it directly inside the layer 2 frame, this leverages IS-IS …

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The endless story of OSPF vs IS-IS – Part 2 “The history”

In our previous post we started consolidating the endless story of OSPF vs IS-IS, in this post we will cover the historical part of the story, it might not be interesting for some people, but I do believe that the history is what makes the future, so please bare with me through this post. The IS-IS protocol was developed in 1987 by Digital Equipment Corporation (DEC) as part of DECnet Phase V. and was standardized later in 1992 by the International Standards Organization (ISO) in ISO/IEC 10589:1992, the second and current edition ISO/IEC 10589:2002 cancels and replaces the first edition. …

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