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Enterasys Networks XSR CLI Router User Manual

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BGP Set Commands

6-114 Configuring the Border Gateway Protocol

Syntax

match ip next-hop access-list-number

Syntax of the “no” Form

Thenoformofthiscommandremovesthematchnexthopvalue:

no match ip next-hop access-list-number

Mode

Route‐mapconfiguration:XSR(config-route-map)#

Default

NomatchingbasedonIPnexthop.

Example

ThefollowingexamplesetsthematchingIPnexthopto10:

XSR(config)#access-list 10 permit 1.2.3.4

XSR(config)#route-map 1 permit 1

XSR(config-route-map)#match ip next-hop 10

BGP Set Commands

Routemapsarecomprisedofsetsofmatchandsetcommands.Matchcommandsdefinethematch

criteriaforroutemaps.Routesthatmatchalldefinedmatchcriteriaareprocessedviaset

commandsandthosethatdonotmatchallofthedefinedmatchcriteriaintheroutemapare

ignored.

set as-path

ThiscommandincreasesthelengthoftheAS‐pathattributefortheBGProutingupdatemessages

thatmeetthematchconditionsspecifiedwithinaroutemap.

ThelengthoftheASpathattributeinfluencestheBGProuteselectionprocessfordestinationsthat

canbereachedbymeansofmultiplepaths.AS

pathlengthistheonlyglobalBGPmetricthatyou

canusetoinfluencebest‐pathselection.ABGPspeakercaninfluencethebestpathselectionbya

peerbyvaryingthelengthoftheASpath.

Ifyoudonotsetlocalpreferenceorweight,ASpathlengthdetermineswhich

ofmultipleroutes

areselected.Routeswithlongerautonomoussystempathsarepreferred.Topreferapath,youcan

padtheautonomoussystempathbyprependingextraautonomoussystemnumbers.

Syntax

set as-path prepend as-path-string

access-list-number

TheACLtomatch,rangingfrom1to199.

prepend

Instructsthesystemtoattachtheas‐path‐stringvaluetotheASpathofthe

routethatmatchestheroutemap.

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