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BGP

BGP Attributes List

BGP Attributes are pieces of information that a BGP router attaches to describe different prefixes included in it’s BGP update messages. There is a variable sequence of BGP attributes in every update message except for those that carries only withdrawn routes. Each attribute is a TLV that consists of attribute …

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BGP Attributes: Local Preference Attribute

The local preference attribute is a well-know discretionary attribute. This means local preference must be recognized by all BGP implementations, but will not exist in all BGP update messages; specifically it will not exist in E-BGP update messages. BGP local preference attribute is one of the most used attributes in …

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BGP Attributes: Atomic Aggregate Atribute

Atomic aggregate is a Well-known Discretionary attribute; it must be recognized by all BGP implementations and does not have to exist in all BGP updates. The purpose of the attribute is to alert BGP speakers along the path that some information have been lost due to the route aggregation process …

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BGP Attribute Types and Flags

BGP attributes is an interesting subject of study.  BGP is a very flexible and extensible protocol and I like that, let’s see how flexible is that protocol when it comes to attributes handling. We all know that BGP has four types of attributes as listed: Well-known mandatory. Well-known discretionary. Optional …

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The Role of BGP in MPLS networks

In almost every book you will read about MPLS, the author will state that one of the MPLS benefits is having a BGP free core network; sometimes they explain it sometimes not. However, to really understand this statement I encourage you to imagine removing MPLS from your core network and …

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BGP Route Refresh Capability

Service Providers or Large enterprises commonly change routing policies from time to time, specially when adding new links or peering relationships with other entities. When you change the inbound policy of your BGP speaker you need to reprocess the updates you received from that peer. BGP4 has no mechanism of …

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