To Next Page

To Previous Page

Selecting Route Paths in BGP

BGPselectsonlyonepathasthebestpath.Itdoesnotrelyonmetricattributesto

determinethebestpath.WhenthesamenetworkislearnedviamorethanoneBGP

peer,BGPusesitspolicyforselectingthebestroutetothatnetwork.TheBGP

implementationonthe CN4093

usesthefollowingcriteriatoselectapathwhenthe

samerouteisreceivedfrommultiplepeers.

1. Localfixedandstaticroutesarepreferredoverlearnedroutes.

2. WithiBGPpeers,routeswithhigherlocalpreferencevaluesareselected .

3. Inthecaseofmultipleroutesofequalpreference,theroutewith

lowerASpath

weightisselected.

ASpathweight=128xASpathlength(numberofautonomoussystemstraversed).

4. Inthecaseofequalweightandrouteslearnedfrompeersthatresideinthesame

AS,thelowermetricisselected.

Note: Aroutewithametricispreferredovera

routewithoutametric.

5. Thelowercosttothe nexthopofroutesisselected.

6. Inthecaseofequalcost,theeBGProuteispreferredoveriBGP.

7. Ifallrouteshavesameroutetype(eBGPoriBGP),theroutewiththelowerrouter

IDisselected .

Whenthepathis

selected,BGPputstheselectedpathinitsroutingtableand

propagatesthepathtoitsneighbors.

Lenovo Flex System Fabric CN4093 User Manual

Other manuals for Lenovo Flex System Fabric CN4093