BGP: Difference between revisions
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= Route Reflector?<ref>www.accenture.com</ref> = |
= Route Reflector?<ref>www.accenture.com</ref> = |
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{{UC}} |
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*Any route received from an iBGP neighbor must not be advertised to any other iBGP neighbor. |
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*This requires all iBGP routers be connected in logical full mesh topology, which is not scalable. |
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Two solution possible: |
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BGP confederations |
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Route reflectors |
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*A route reflector is BGP router that is allowed to break the iBGP loop avoidance rule. |
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*Route reflectors can advertise updates received from an iBGP peer to another iBGP peer. |
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*This allow for building iBGP networks that scale easily. |
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*IBGP routers are divided into: |
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Route Reflectors |
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Route Reflector Clients |
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Non-Client Peers |
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*Routes received from: |
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Route-Reflector-client is reflected to other clients and non-client neighbors |
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Non-client neighbors are reflected to Route-Reflector-client neighbors only |
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*Sets the '''Originator-ID''' attribute in the reflected update if it is not already set. |
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*Adds the Cluster-ID to the Cluster-list attribute in the reflected update. |
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*RR reflects routes considered as best routes only. |
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*If more than one update is received for the same destination only the BGP best route is reflected. |
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*RR is not allowed to change any attributes of the reflected routes including the next-hop attribute. |
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*Loop Prevention: |
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If a router received an iBGP route with the Originator-ID attribute set to its own router-id, the route is discarded. |
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If a route reflector receives a route with a cluster-list attribute containing its cluster-id, the route is discarded. |
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*Config: |
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;RR1 router: |
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router bgp 100 |
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neighbor 172.16.1.2 remote-as 100 |
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neighbor 172.16.1.2 route-reflector-client |
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neighbor 172.16.1.2 description Client1 |
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;Client1 router: |
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router bgp 100 |
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neighbor 172.16.1.1 remote-as 100 |
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neighbor 172.16.1.1 description RR1 |
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network 11.1.1.1 mask 255.255.255.255 --> Route to be reflected |
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= Confederation = |
= Confederation = |