BGP: Difference between revisions
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;Multi-Exit Discriminator |
;Multi-Exit Discriminator |
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*The MED is an optional attribute that comes in handy when there are multiple entrance paths to an AS. |
* The MED is an optional attribute that comes in handy when there are multiple entrance paths to an AS. |
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*The remote AS sets MED values to tell the other AS which path to use. |
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*The |
* The remote AS sets MED values to tell the other AS which path to use. |
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* The MED is passed between the two autonomous systems, but the value is not passed to any other ASs. |
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*The path with the lowest MED is the preferred path. |
* The path with the lowest MED is the preferred path. |
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*This attribute is only used to influence entry INTO the AS. |
* This attribute is only used to influence entry INTO the AS. |
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;Local Preference |
;Local Preference |
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* Local Preference is configured in Incoming direction. |
* Local Preference is configured in Incoming direction. |
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* Configure Local Pref R3 so that R1 will prefer routes learned via R3. |
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* Local Pref stays inside AS only(use MED if you want to affect AS also). |
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* Configured for the whole BGP process on the router. |
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;Weight: |
;Weight: |
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;Example |
;Example Scenario: |
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<--AS3--> <--AS100--> |
<--AS3--> <--AS100--> |
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|------[R2]--------[R4] |
|------[R2]--------[R4] |
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|------[R3]--------[R5] |
|------[R3]--------[R5] |
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Weight R1 to R2 or R3: |
* Weight R1 to R2 or R3: |
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|------> |
|------> |
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Local Preference R2 to R1 or R3 to R1: |
* Local Preference R2 to R1 or R3 to R1: |
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<------| |
<------| |
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MED R4 to R2 or R5 to R3: |
* MED R4 to R2 or R5 to R3: |
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|---------> |
|---------> |
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