CCIE – STP 802.1D – Fundamentals

INTRODUCTION For resiliency purposes, Layer2 topologies are designed and deployed in a physical loop. Unlike the IP protocol which uses the TTL field as a built-in mechanism for preventing packets from looping endlessly through the network, the Ethernet protocol does not provide such facility and therefore, unless we can prevent a layer2 loop, the following problems would occur: Broadcast storms – endless broadcast of frames through the entire L2 domain Hosts end-up receiving duplicates frames from different switches Unstable mac-address tables due to continuous host mac address learning on different ports The STP (Spanning Tree Protocol) was developed to avoid…

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BGP Attributes and BGP Path Selection

In this blog I will briefly review the BGP path selection algorithm used when deciding which BGP routes to install in the routing table. Though before doing so, I ought to review first the BGP attributes. BGP ATTRIBUTES TYPES Firstly, we classify BGP attributes based on whether or not they should be supported within a specific vendor BGP implementation. Well-Known BGP attributes are supported in all BGP implementation regardless the vendor. Depending on whether or not these are sent with BGP Updates, we further classify them into: Mandatory attributes – these must be present in every single update where NLRIs…

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