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Wael Osama

Link state protocols and Areas concept

Link state protocols have introduced the concept of multiple routing areas withing the same routing domain. Link state protocols depend on the fact that all routers must have an identical link state database and then each router will start calculating its very own routing table from this information. However, this rule sometimes introduce scalability limitations to network designers. In very large networks all routers must maintain the same link state database; this induces some scalability limitations in these networks.

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Black hole filtering

Black hole filtering is a technique usually used by service providers for traffic filtering without applying access-lists. The technique is very useful in mitigation of many types of DOS attacks. The idea behind Black hole filtering is very simple; just define the traffic you want to discard and configure a static route pointing to the Null0 interface. The following rules summarize the technique: Define the suspected traffic by destination. Configure static route pointing this destination to null0. Black hole filtering is based on the destination address of the packet. Packets directed to the Null interface are just discarded. Static routes …

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VRF Lite

The word VRF stands for Virtual Routing and Forwarding, this feature is used to create multiple instances of the routing table on the same routing device. VRFs are usally used in conjunction with MPLS VPN to separate the traffic of multiple MPLS VPN customers. VRF Lite feature is part of Cisco’s network virtualization portfolio. VRF Lite means VRF without  the need to run MPLS in the network.  VRF Lite allows the network administrator to create multiple routing instances on the same routing device within the enterprise. VRF Lite can be useful when you need to isolate traffic between two networks …

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BGP Route Reflector Basics

Everyone who ever studied BGP knows that BGP has strong rules to prevent routing and updates loops. In this post I will focus on iBGP loop prevention and specifically route reflectors as a result. The rule states: that any route received from an iBGP neighbor must not be advertised to any other iBGP neighbor. This loop prevention mechanism induces a requirement that all iBGP routers in the network should be connected in logical full mesh topology to allow for routing information propagation through out the network. However, full mesh connectivity has never been a scalable solution specially in large networks. Two mechanisms …

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Interview with Emmanuel Conde

Today I have a special treat for you — an exclusive written interview with the CCIE Agent Emmanuel Conde. Eman (Emmanuel Conde) has the distinction of being the only CCIE recruiter promoted by World Wide Channels of Cisco Systems.   Eman earned this distinction because of his tireless efforts on behalf of CCIEs and developing Cisco talent.  He has spoken at Cisco Academy events, developed an international CCIE mentor program, writes for ITWorld magazine, has a very active blog focused on CCIE career concerns, and produces the CCIE Flyer an online magazine published monthly.  He has developed a unique approach to …

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ARP Caching and Timeout

From time to time I find myself craving to the fundamentals; I do this for two main reasons, the first one is that fundamentals are the building blocks of all complex networking topics and deeply understanding them makes a better engineer, the second one is longing to simplicity after doing some complex tasks. One of these fundamentals that is worth reviewing is the Address Resolution Protocol, this protocol is one of the main building blocks of any network existing on earth today.

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