BGP: Difference between revisions
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= Confederation = |
= Confederation = |
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*RR does not require major changes to existing configuration |
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*It implies choosing routers that will act as a focal point for iBGP sessions within a single AS, running a single IGP. |
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*Confederations needs quite a config change and architecture. |
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*Confederations may contain different IGPs, adding more flexibility to scaling your network. |
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*In case your IGP is exceeding its scalability limit and becomes unmanageable, use Confederation. |
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*A method to subdivide a single AS into multiple internal sub-AS's, yet still advertise as a single AS to external peers. |
*A method to subdivide a single AS into multiple internal sub-AS's, yet still advertise as a single AS to external peers. |
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*The intent is to reduce iBGP mesh size. |
*The intent is to reduce iBGP mesh size, scalable approach for a large autonomous system. |
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*Each of Sub-AS has its own AS number. |
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*Reduces the total number of iBGP peering sessions per router within AS. |
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*Large no of iBGP sessions can consume bandwidth and cause high CPU utilization, so negatively affect the performance. |
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*Each sub-AS has different AS number. |
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*All peers in sub-AS are fully meshed in order to learn external routes from external sources. |
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*Every sub-AS is identified by its unique AS number(private: 64512 – 65535), the connection between them is always eBGP peering called Intra-Confederation eBGP. |
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*eBGP routes between sub-ASs called Confederation External Routes, are preferred over iBGP routes. |
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*If BGP has to choose between two paths, one leading inside sub-AS and other outside sub-AS, within confederation, it will choose the external path – to neighboring sub-AS. |
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*To choose between Confederation eBGP route and eBGP route leading outside of confederation, BGP will choose the second one. |
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*AS_PATH attribute contains AS_CONFED_SET parameter which is modified inside the confederation only |
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*In case the confederation runs one IGP, NEXT_HOP, MED, LOCAL_PREF do not change when routing update traverses Intra-Confederation eBGP |
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= Route Aggregation = |
= Route Aggregation = |