Cisco Ccnp Certification The Bgp Weight Attribute

Cisco Ccnp Certification The Bgp Weight Attribute



Cisco CCNP Certification: the​ BGP Weight Attribute
When you're studying for the​ CCNP certification,​ especially the​ BSCI exam,​ you must gain a​ solid understanding of​ BGP .​
BGP isn't just one of​ the​ biggest topics on​ the​ BSCI exam,​ it's one of​ the​ largest .​
BGP has a​ great many details that must be mastered for BSCI success,​ and those of​ you with one eye on​ the​ CCIE must learn the​ fundamentals of​ BGP now in​ order to​ build on​ those fundamentals at​ a​ later time.
Path attributes are a​ unique feature of​ BGP .​
With interior gateway protocols such as​ OSPF and EIGRP,​ administrative distance is​ used as​ a​ tiebreaker when two routes to​ the​ same destination had different next-hop IP addresses but the​ same prefix length .​
BGP uses path attributes to​ make this choice.
The first attribute considered by BGP is​ weight .​
Weight is​ a​ Cisco-proprietary BGP attribute,​ so if​ you're working in​ a​ multivendor environment you should work with another attribute to​ influence path selection.
The weight attribute is​ significant only to​ the​ router on​ which it​ is​ changed .​
If you set a​ higher weight for a​ particular route in​ order to​ give it​ preference (a higher weight is​ preferred over a​ lower one),​ that weight is​ not advertised to​ other routers.
BGP uses categories such as​ transitive,​ non-transitive,​ mandatory,​ and optional to​ classify attributes .​
Since weight is​ a​ locally significant Cisco-proprietary attribute,​ it​ does not all into any of​ these categories.
The weight can be changed on​ a​ single route via a​ route-map,​ or​ it​ can be set for a​ different weight for all routes received from a​ given neighbor .​
To change the​ weight for all incoming routes,​ use the​ weight option with the​ neighbor command after forming the​ BGP peer relationships.
R2(config)#router bgp 100
R2(config-router)#neighbor 100.1.1.1 remote-as 10
R2(config-router)#neighbor 100.1.1.1 weight 200
Learning all of​ the​ BGP attributes,​ as​ well as​ when to​ use them,​ can seem an​ overwhelming task when you first start studying for your BSCI and CCNP exams .​
Break this task down into small parts,​ learn one attribute at​ a​ time,​ and soon you'll have the​ BGP attributes mastered.




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