BSCI20S07L01.pps - Building Scalable Cisco Internetworks(BSCI Instructor Name MR.SIDDIQ AHMED CCIE 17864 BORDER GATEWAY PROTOCOL BSCI 2.0\u20147-2 BGP

BSCI20S07L01.pps - Building Scalable Cisco...

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Building Scalable Cisco Internetworks (BSCI) Instructor Name MR.SIDDIQ AHMED CCIE # 17864
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BSCI 2.0—7-2 BORDER GATEWAY PROTOCOL
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BSCI 2.0—7-3 BGP Characteristics BGP is most appropriate when at least one of the following conditions exists: An AS allows packets to transit through it to reach other Autonomous Systems (e.g., a service provider). An AS has multiple connections to other Autonomous Systems. Routing policy and route selection for traffic entering and leaving your AS must be manipulated. BGP is not always appropriate. Do not use BGP if you have one of the following conditions: Single connection to the Internet or other AS Lacks memory or processor power to handle constant updates on BGP routers Limited understanding of route filtering and BGP path selection process Low bandwidth between Autonomous Systems
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BSCI 2.0—7-4 BGP Characteristics (Cont) : BGP is a path-vector protocol with the following enhancements over distance vector protocols: Reliable updates: BGP runs on top of TCP (port 179) Incremental, triggered updates only Periodic keepalives messages to verify TCP connectivity (The BGP sends BGP/TCP keepalives by default every 60 seconds) Rich metrics (called path vectors or attributes) Designed to scale to huge internetworks (e.g., the Internet)
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BSCI 2.0—7-5 What Is Multihoming? Connecting to two or more ISPs to increase: Reliability—If one ISP or connection fails, there is still Internet access Performance—Better path selection to common Internet destinations
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BSCI 2.0—7-6 Perform Multihoming with BGP: Following are three common ways to configure the connections: Default routes from all providers Pass default route to internal routers Provider-owned routes and the default route from each provider Redistribute into Interior Gateway Protocol (IGP) for internal routers, or Run BGP on all routers in the AS Full routes from all providers Run BGP on all internal routers; turn off BGP synchronization
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BSCI 2.0—7-7 BGP Databases Neighbor table List of BGP neighbors BGP forwarding table/database List of all networks learned from each neighbor Can contain multiple pathways to destination networks Database contains BGP attributes for each pathway IP routing table List of best paths to destination networks. [EBGP ROUTES (ROUTES LEARNED FROM AN EXTERNAL AS) HAVE AN AD VALUE 20] [IBGP ROUTES (ROUTES LEARNED FROM WITHIN THE AS) HAVE AN AD VALUE 200]
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BSCI 2.0—7-8 BGP Message Types BGP defines the following message types: Open Includes holdtime and BGP router ID Keepalive Update Information for one path only (could be to multiple networks) Includes path attributes and networks Notification When error is detected BGP connection is closed after sent
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BSCI 2.0—7-9 BGP Autonomous Systems An AS is a collection of networks under a single technical administration.
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  • Summer '20
  • Border Gateway Protocol, BGP routers, BGP Autonomous Systems

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