BGP Overview

Border Gateway Protocol ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

BGP: Why do we need it? ,[object Object],[object Object],[object Object],[object Object]

Who would invent such a thing? Yakov Rekhter – Juniper Networks Formerly of cisco and IBM Kirk Lougheed - cisco

BGP Over the Years ,[object Object],[object Object]

Yakov Mania! ,[object Object],[object Object],[object Object],[object Object],Since most people are not familiar with Yakov Rekhter, it is only fitting that he receive his own slide. Why? Bill Gates gets all the adoration from the systems people and network people need their own hero.

Autonomous System (AS) ,[object Object],Source: http://en.wikipedia.org/wiki/Autonomous_system_(Internet)

Choose The Right Path BGP routing table entry for 68.156.159.0/24 Paths: (13 available, best #9, table Default-IP-Routing-Table) Advertised to non peer-group peers: 195.28.164.125 3333 6320 2828 29766 193.0.0.56 from 193.0.0.56 (193.0.0.56) Origin IGP, localpref 100, valid, external Community: 6320:21000 6320:21310 Last update: Sat Sep 12 00:54:11 2009 34225 1299 2828 29766 193.138.164.1 from 193.138.164.1 (193.138.164.1) Origin IGP, localpref 100, valid, external Community: 34225:1000 34225:1001 Last update: Fri Sep 11 12:51:30 2009 1930 20965 3549 2828 29766 193.136.5.1 from 193.136.5.1 (193.136.5.1) Origin IGP, localpref 100, valid, external Last update: Fri Sep 11 10:28:59 2009 42109 41965 41877 12389 8342 2828 29766 91.103.24.1 from 91.103.24.1 (91.103.24.1) Origin EGP, localpref 100, valid, external Last update: Fri Sep 11 09:55:24 2009

Connecting AS’es ,[object Object],[object Object],[object Object],[object Object],[object Object]

How Do I Affect Traffic Flow? ,[object Object],[object Object],[object Object],[object Object],BGP has many attributes that can be used to affect traffic flow. They will fall into 1 of 4 different categories:

Well Known Mandatory Must be understood by all BGP speakers, and must be included in all update messages.

Well Known Discretionary Must be understood by all BGP speakers, and can be carried in updates, but are not required.

Optional Transitive May be understood by some BGP speakers, but not all. They need to be included in updates and advertised to all peers whether they understand them or not.

Optional Non-Transitive May be understood by some BGP speakers, but not all. If these attributes are not understood, they are dropped and not advertised to peers.

Origin - WKM ,[object Object],[object Object],[object Object],[object Object],[object Object]

AS Path - WKM ,[object Object],[object Object],[object Object],[object Object],[object Object]

Next Hop - WKM ,[object Object],[object Object]

Multi-Exit Discriminatory(MED) - ONT ,[object Object]

Local Preference - WKD ,[object Object],[object Object]

Atomic Aggregate - WKD ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Additional BGP Concepts ,[object Object],[object Object],[object Object],[object Object],And last but not least……..

Route Reflectors What if your AS looked like this? In iBGP, all speakers must have a neighbor relationship with each other to prevent routing loops. In a 10 router AS, you would have to configure 9 neighbors per router for a total of 45 neighbor relationships based on (n–(n–1))/2.

Route Reflectors With route reflectors, your AS could look like this. A lot fewer iBGP neighbor relationships would be required. RR – Route Reflector RRC – Route Reflector Client NCP – Non-Client Peer

Additional Resources ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Routing TCP/IP Volume II By Jeff Doyle and Jennifer DeHaven Carroll Cisco Press ISBN-13: 978-1578700899

Additional Resources ,[object Object],[object Object],[object Object],[object Object],[object Object]

Additional Resources ,[object Object],[object Object],[object Object]

BGP Overview

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BGP Overview