BGP: Difference between revisions
Content added Content deleted
Line 81: | Line 81: | ||
Routing Table List of Best Routes |
Routing Table List of Best Routes |
||
= |
= Attributes<ref>www.accenture.com</ref>= |
||
Mnemonics: [[Mnemonics|N-WLLA-OMNI]] |
Mnemonics: [[Mnemonics|N-WLLA-OMNI]] |
||
Line 87: | Line 87: | ||
*It uses the BGP Best Path Selection Algorithm to do this. |
*It uses the BGP Best Path Selection Algorithm to do this. |
||
*Routes installed by different BGP instances are compared by the general algorithm, i.e. route distances are compared and the route with lower distance is preferred. |
*Routes installed by different BGP instances are compared by the general algorithm, i.e. route distances are compared and the route with lower distance is preferred. |
||
Well known BGP attribute types: |
|||
Well-known mandatory: Attributes of this type must be understood by all BGP implementations and must EXIST in the BGP update messages. |
|||
Well-known discretionary: Attributes of this type must be understood by all BGP implementations but they don’t have to exist in all BGP updates to all neighbors. |
|||
Optional BGP attribute types: |
|||
Optional transitive: optional BGP attributes as the name implies don’t need to be understood by all BGP implementations, but since the transitive flag is set they will be passed to other neighbors. |
|||
Optional non-transitive: Attributes of this type are also optional as the name implies and will not be passed to other neighbors. |
|||
<center> |
<center> |
||
Line 93: | Line 102: | ||
! Attribute !! Which is better |
! Attribute !! Which is better |
||
|- |
|- |
||
|Next Hop reachable || Route cannot be used if next hop is unreachable |
|Next Hop reachable || Route cannot be used if next hop is unreachable || Well-known Mandatory |
||
|- |
|- |
||
|Weight || Bigger |
|Weight || Bigger |
||
|- |
|- |
||
|Local Preference || Bigger |
|Local Preference || Bigger || Well-known discretionary |
||
|- |
|- |
||
|Locally Injected || Locally injected is better than iBGP/eBGP learned |
|Locally Injected || Locally injected is better than iBGP/eBGP learned |
||
|- |
|- |
||
|AS Path Length || Smaller |
|AS Path Length || Smaller || Well-known mandatory |
||
|- |
|- |
||
|Origin || Prefer IGP(network cmd) > EGP > ?(reditributed) |
|Origin || Prefer IGP(network cmd) > EGP > ?(reditributed) || Well-known Mandatory |
||
|- |
|- |
||
|MED(Metric) || Smaller |
|MED(Metric) || Smaller || Optional non-transitive |
||
|- |
|- |
||
|Neighbor Type || Prefer eBGP over iBGP |
|Neighbor Type || Prefer eBGP over iBGP |