ccie课程就业路由

BGP

边界网关路由协议Implementing

BGPExplaining

BGP

Concepts

andTerminologyUsing

BGP

to

Connect

to

the

InternetWhat

Is

Multihoming?Connecting

to

two

or

more

ISPs

to

increase

thefollowing:Reliability:

If

one

ISP

or

connection

fails,

thereis

still

Internet

access.Performance:

Path

selection

to

commonInternet

destinations

is

better.Example:

Default

Routes

fromAllProvidersDefault

Routes

from

All

Providersand

Partial

TableExample:

Full

Routes

fromAllProvidersBGP

Autonomous

SystemsAn

AS

is

a

collection

of

networks

under

a

singletechnicaladministration.IGPs

operate

within

an

AS.BGP

is

used

between

autonomoussystems.Exchange

of

loop-free

routing

information

is

guaranteed.BGP

Path-Vector

RoutingIGPs

announce

networks

and

describe

the

metric

toreach

those

networks.BGP

announces

paths

and

the

networks

that

arereachable

at

the

end

of

the

path.

BGP

describes

thepath

by

using

attributes,

which

are

similar

to

metrics.BGP

allows

administrators

to

define

policies

or

rules

forhow

data

will

flow

through

the

autonomous

systems.BGP

Routing

PoliciesBGP

can

support

any

policy

conforming

to

the

hop-by-hop

(AS-by-AS)

routing

paradigm.BGP

CharacteristicsBGP

is

most

appropriate

when

at

least

one

of

the

followingconditionsexists:An

AS

allows

packets

to

transit

through

it

to

reach

other

autonomoussystems

(for

example,

it

is

a

service

provider).An

AS

has

multiple

connections

to

other

autonomous

systems.Routing

policy

and

route

selection

for

traffic

entering

and

leaving

theAS

must

be

manipulated.BGP

isnotalways

appropriate.Youdonothave

to

use

BGP

if

youhaveone

of

the

following

conditions:Limited

understanding

ofroute

filtering

and

BGP

path-selection

processA

single

connection

to

the

Internet

or

another

ASLack

of

memory

or

processor

power

to

handle

constantupdates

on

BGP

routersBGP

Characteristics

(Cont.)BGP

is

a

path-vector

protocol

with

the

followingenhancements

over

distance

vector

protocols:Reliable

updates:

runs

on

top

of

TCP

(port

179)Incremental,

triggered

updates

onlyPeriodic

keepalive

messages

to

verify

TCPconnectivityRich

metrics

(called

path

vectors

or

attributes)Designed

to

scale

to

huge

internetworks

(forexample,

the

Internet)BGPDatabasesNeighbor

tableList

of

BGP

neighborsBGP

table

(forwarding

database)List

of

all

networks

learned

from

each

neighborCan

contain

multiple

paths

to

destination

networksContains

BGP

attributes

for

each

pathIP

routing

tableList

of

best

paths

to

destination

networksBGP

Message

TypesBGP

defines

the

following

message

types:OpenIncludes

hold

time

and

BGP

router

IDKeepaliveUpdateInformation

for

one

path

only(could

be

to

multiple

networks)Includes

path

attributes

and

networksNotificationWhen

error

is

detectedBGP

connection

closed

after

message

is

sentSummaryIf

your

network

is

multihomed—has

more

than

oneconnection

to

the

Internet—then

using

BGP

to

connectto

your

ISPs

may

be

appropriate.Multihoming

options

include

having

each

ISP

passthese:Only

a

default

routeA

default

route

and

provider-owned

specificroutesAll

routesBGP

is

the

external

routing

protocol

used

betweenautonomous

systems.

Forwarding

is

based

on

policyand

not

on

best

path.BGP

状态机Open-sentOpen-confirmEstablishedIdleConnect重连计时器超时TCP连接失败重连计时器超时开始其它TCP连接失败错误错误错误KeepAlive计时器超时接收到KeepAlive消息接收到正确的OPEN报文TCP连接建立TCP连接建立其它ActiveTCP连接失败KeepAlive计时器周期更新BGP数据库IP路由表(IP-RIB)全局路由信息库，包括所有IP路由信息。BGP路由表(Loc-RIB)BGP路由信息库，包括本地BGPSpeaker选择的路由信息。邻居表对等体邻居清单列表Adj-RIB-In对等体宣告给本地Speaker的未处理的路由信息库Adj-RIB-Out本地Speaker宣告给指定对等的路由信息库BGP路由信息处理Adj-RIB-Out输入策略引擎Loc-RIBIP-RIB输出策略引擎从对等体来的更新信息向对等体发送的更新信息①Adj-RIB-In②路径选择③④⑤Summary

(Cont.)BGP

routers

exchange

network

reachability

informationcalled

path

vectors,

made

up

of

path

attributes.

The

path-vector

information

includes

a

list

of

the

full

path

of

BGP

ASnumbers

necessary

to

reach

a

destination

network.A

router

running

BGP

keeps

its

own

tables

to

storeBGPinformation

that

it

receives

from

and

sends

to

otherrouters,including

a

neighbor

table,

a

BGP

table

(also

called

aforwarding

database

or

topology

database),

and

anIProuting

table.There

are

four

BGP

message

types:

open,

keepalive,

update,and

notification.Implementing

BGPExplainingEBGP

and

IBGPPeers

=

NeighborsA

“BGP

peer,”

also

known

as

a

“BGP

neighbor,”

isaspecific

term

that

is

used

for

BGP

speakers

that

haveestablished

a

neighbor

relationship.Any

two

routers

that

have

formed

a

TCP

connection

toexchange

BGP

routing

information

are

called

BGP

peersor

BGP

neighbors.External

BGPWhen

BGP

is

running

between

neighbors

that

belongto

different

autonomous

systems,

it

is

called

EBGP.EBGP

neighbors,

by

default,

need

to

be

directlyconnected.Internal

BGPWhen

BGP

is

running

between

neighbors

within

thesame

AS,

it

is

called

IBGP.The

neighbors

do

not

have

to

be

directly

connected.IBGP

in

a

Transit

AS

(ISP)Redistributing

BGP

into

an

IGP

(OSPF

in

this

example)

isnot

mended.Instead,

run

IBGP

on

all

routers.IBGP

in

a

NonTransit

ASBy

default,

routes

learned

via

IBGP

are

never

propagated

to

other

IBGPpeers,

so

they

need

full-mesh

IBGP.Routing

Issues

If

BGP

Noton

in

AllRouters

in

Transit

PathRouter

C

will

drop

the

packet

to

network

10.0.0.0.

Router

C

is

notrunning

IBGP;

therefore,it

has

not

learned

about

the

route

to

network10.0.0.0

from

router

B.In

this

example,

router

B

and

router

E

are

not

redistributingBGP

intoOSPF.SummaryThe

key

terms

to

describe

relationships

between

routers

runningBGP

are

asfollows:BGPspeaker,

or

BGP

routerBGP

peer,

or

neighborIBGP

and

EBGPEBGP

neighbors

are

directly

connected

routers

in

differentautonomous

systems.IBGP

neighbors

are

routers

in

the

same

AS

that

are

reachablebystatic

routes

or

a

dynamic

internal

routing

protocol.All

routers

in

the

transit

path

within

an

AS

should

runfully

meshed

IBGP.Implementing

BGPConfiguring

Basic

BGP

OperationsBGPCommandsrouter

bgp

autonomous-systemRouter(config)#This

command

enters

router

configuration

mode

only; mandsmustbe

entered

to

activate

BGP.Only

one

instance

of

BGP

can

be

configured

on

the

router

at

a

singletime.The

autonomous

system

number

identifies

the

autonomous

systemto

which

the

router

belongs.The

autonomous

system

number

in

this

command

is

compared

to

theautonomous

system

numbers

listed

in

neighbor

statements

todetermine

if

the

neighbor

is

an

internal

or

external

neighbor.BGP

neighborremote-asCommandneighbor

{ip-address

|

peer-group-name}remote-as

autonomous-systemRouter(config-router)#The

neighbor

command

activates

a

BGP

session

with

this

neighbor.The

IP

address

that

is

specified

is

the

destination

address

of

BGPpackets

going

to

this

neighbor.This

router

must

have

an

IP

path

to

reach

this

neighborbefore

it

can

set

up

a

BGP

relationship.The

remote-as

option

shows

what

AS

this

neighbor

is

in.

This

ASnumber

is

used

to

determine

if

the

neighbor

is

internal

or

external.This

command

is

used

for

both

external

and

internal

neighbors.Example:

BGP

neighbor

CommandBGP

neighbor

shutdown

Commandneighbor

{ip-address

|

peer-group-name}

shutdownRouter(config-router)#no

neighbor

{ip-address

|

peer-group-name}

shutdownAdministratively

brings

downa

BGP

neighborUsed

for

maintenance

and

policy

changes

to

preventroute

flappingRouter(config-router)#Re-enables

a

BGP

neighbor

that

has

been

administratively

shutdownBGP

Issues

with

Source

IP

AddressWhen

creating

a

BGP

packet,

the

neighbor

statementdefines

the

destination

IP

address

and

the

outboundinterface

defines

the

source

IP

address.When

a

BGP

packet

is

received

for

a

new

BGP

session,the

source

address

of

the

packet

is

compared

to

the

listof

neighbor

statements:If

a

match

is

found,

a

relationship

is

established.If

no

match

is

found,

the

packet

is

ignored.Make

sure

that

the

source

IP

address

matches

theaddress

that

the

other

router

has

in

its

neighborstatement.Example:

IBGP

Peering

IssueBGP

neighbor

update-sourceCommandneighbor

{ip-address

|

peer-group-name}

update-sourceinterface-type

interface-numberRouter(config-router)#This

command

allows

the

BGPprocess

to

use

the

IP

address

of

a

specifiedinterface

as

the

source

IP

address

of

all

BGP

updates

to

that

neighbor.A

loopback

interface

is

usually

used,

because

it

will

be

available

as

long

asthe

router

is

operational.The

IP

address

used

in

the

neighbor

command

on

the

other

router

will

bethe

destination

IP

address

of

all

BGP

updates

and

should

be

the

loopbackinterface

of

this

router.The

neighbor

update-source

command

is

normally

used

only

with

IBGPneighbors.The

address

of

an

EBGPneighbor

must

be

directly

connected

bydefault;

the

loopback

of

an

EBGP

neighbor

is

not

directly

connected.Example:

BGP

Using

Loopback

AddressesBGP

neighbor

ebgp-multihopCommandneighbor

{ip-address

|

peer-group-name}

ebgp-multihop

[ttl]Router(config-router)#This

command

increases

the

default

of

one

hop

for

EBGP

peers.It

allowsroutes

to

the

EBGP

loopback

address(which

willhave

a

hop

count

greater

than

1).Example:

ebgp-multihopCommandNext-Hop

BehaviorBGP

is

an

AS-by-ASrouting

protocol,

not

a

router-by-routerroutingprotocol.In

BGP,

the

next

hop

does

not

mean

the

next

router;it

means

the

IPaddress

to

reach

the

next

AS.For

EBGP,

the

default

next

hop

is

the

IP

address

of

the

neighbor

routerthat

sent

theupdate.For

IBGP,

the

BGP

protocol

states

that

the

next

hop

advertised

by

EBGPshould

be

carriedinto

IBGP.Example:

Next-Hop

BehaviorRouter

A

advertisesnetwork

172.16.0.0

torouter

B

in

EBGP,

witha

next

hop

of10.10.10.3.Router

B

advertises172.16.0.0

in

IBGP

torouter

C,

keeping10.10.10.3as

the

next-hopaddress.BGP

neighbor

next-hop-selfCommandForces

all

updates

for

this

neighbor

to

beadvertised

with

this

router

as

the

next

hop.The

IP

address

used

for

the

next-hop-self

option

will

bethe

same

as

the

source

IP

address

of

the

BGP

packet.neighbor

{ip-address

|

peer-group-name}

next-hop-selfRouter(config-router)#Example:

next-hop-selfConfigurationThe

following

takes

place

in

amultiaccess

network:Router

B

advertisesnetwork

172.30.0.0

torouter

A

in

EBGPwitha

next

hop

of

10.10.10.2,not

10.10.10.1.

Thisavoidsanunnecessary

hop.BGP

is

being

efficient

byinforming

AS

64520

ofthebest

entry

point

into

AS

65000for

network

172.30.0.0.Router

B

in

AS

65000

also

advertises

to

AS

64520

thatthe

best

entry

point

for

each

network

in

AS

64600

is

thenext

hop

of

router

C

becausethat

is

the

best

path

tomove

through

AS

65000

to

AS

64600.Example:

Next

Hop

on

a

MultiaccessNetworkneighbor

peer-group-name

peer-groupRouter(config-router)#Using

a

Peer

Groupneighbor

ip-address

peer-group

peer-group-nameThis

command

creates

a

peer

group.Router(config-router)#This

command

defines

a

template

with

parameters

set

for

a

group

ofneighbors

instead

of

individually.This

command

is

useful

when

many

neighbors

have

the

sameoutboundpolicies.Members

can

have

a

different

inbound

policy.Updates

are

generated

once

per

peer

group.Configuration

is

simplified.Router

C

Using

a

PeerGroupRouter

C

Without

a

Peer

Grouprouter

bgp

65100neighbor

192.168.24.1

remote-as

65100neighbor

192.168.24.1

update-source

Loopback

0neighbor

192.168.24.1

next-hop-selfneighbor

192.168.24.1

distribute-list

20

outneighbor

192.168.25.1

remote-as

65100neighbor

192.168.25.1

update-source

Loopback

0neighbor

192.168.25.1

next-hop-selfneighbor

192.168.25.1

distribute-list

20

outneighbor

192.168.26.1

remote-as

65100neighbor

192.168.26.1

update-source

Loopback

0neighbor

192.168.26.1

next-hop-selfneighbor

192.168.26.1

distribute-list

20

outrouter

bgp

65100neighbor

internal

peer-groupneighbor

internal

remote-as

65100neighbor

internal

update-source

Loopback

0neighbor

internal

next-hop-selfneighbor

internal

distribute-list

20

outneighbor

192.168.24.1

peer-group

internalneighbor

192.168.25.1

peer-group

internalneighbor

192.168.26.1

peer-group

internalExample:

Using

a

Peer

GroupBGP

network

Commandnetwork

network-number

[mask

network-mask]

[route-mapmap-tag]Router(config-router)#This

command

tells

BGP

what

network

to

advertise.The

command

does

not

activate

the

protocol

on

an

interface.Without

a

mask

option,

the

command

advertises

classful

networks.

Ifa

subnet

of

the

classful

network

exists

in

a

routing

table,

the

classfuladdress

is

announced.With

the

mask

option,

BGP

looks

for

an

exact

match

in

thelocalrouting

table

before

announcing

the

route.Example:

BGP

network

Commandnetwork

192.168.1.1

mask

255.255.255.0Router(config-router)#network

192.168.0.0

mask

255.255.0.0The

router

looks

for

exactly

192.168.1.1/24

in

the

routing

table,

butcannot

find

it,

so

it

willnot

announceanything.Router(config-router)#The

router

looks

for

exactly

192.168.0.0/16

in

the

routing

table.If

the

exact

route

is

not

in

the

table,

you

can

add

a

static

route

tonull0so

that

the

route

can

beannounced.BGP

SynchronizationsynchronizationEnables

BGP

synchronization

so

that

a

router

will

notadvertiseroutes

in

BGP

until

it

learns

them

in

an

IGPno

synchronizationSynchronization

rule:

Do

not

use

or

advertise

to

an

externalneighbor

a

route

learned

by

IBGP

until

a

matching

route

hasbeen

learned

from

an

IGPEnsures

consistency

of

information

throughout

the

ASSafe

to

have

it

off

only

if

all

routers

in

the

transitpath

in

the

AS

are

running

full-mesh

IBGP;

off

by

default

in

Cisco

IOS

software

release

12.2(8)T

and

laterRouter(config-router)#Disables

BGP

synchronization

so

that

a

router

will

advertise

routes

inBGP

without

learning

them

in

an

IGPRouter(config-router)#Example:

BGP

SynchronizationIf

synchronizationis

on,

then:–

Routers

A,

C,

and

D

would

not

use

or

advertise

the

route

to172.16.0.0

until

they

receive

the

matching

route

via

an

IGP.–

Router

E

would

not

hear

about

172.16.0.0.If

synchronization

isoff(the

default),then:Routers

A,

C,

and

D

would

use

and

advertise

the

route

that

theyreceive

via

IBGP;

router

E

would

hear

about

172.16.0.0.If

router

E

sends

traffic

for

172.16.0.0,

routersA,

C,

and

Dwouldroute

the

packets

correctly

to

router

B.Example:

BGP

ConfigurationBGP

Example

ConfigurationRouterB(config)#

router

bgp

65000RouterB(config-router)#

neighbor

10.1.1.2

remote-as

645203.

RouterB(config-router)#neighbor192.168.2.2remote-as650004.

RouterB(config-router)#neighbor192.168.2.2update-source

Loopback05.

RouterB(config-router)#neighbor192.168.2.2next-hop-self6.

RouterB(config-router)#network172.16.10.0

mask

255.255.255.07.

RouterB(config-router)#network192.168.1.08.

RouterB(config-router)#network192.168.3.09.

RouterB(config-router)#

no

synchronizationBGPStatesWhen

establishing

a

BGP

session,

BGP

goes

through

the

followingstates:1.

idle初始连接重试时间为60秒,以后每次连接重试时间是之前的两倍2.

active

主动尝试建立TCP连接,如果成功将向邻居发送OPEN消息,并迁移至OPENSENT状态,保持定时器被设置为4分钟3.connect该状态等待TCP的连接,如果仍处于连接状态,则重置定时器.并迁移至ACITIVE状态4.opensent

该状态下已经发送了OPEN消息,并侦听来自邻居的OPEN消息,当收到邻居的OPEN消息后,检查每个字段,如果存在差错,则发送notification消息,并迁移至idle状态.如果没有差错则发送keepalive消息,并设置keepalive消息定时器,此外还要协商保持时间.5.

openconfirm该状态下将等待keepalive消息或notification消息,如果收到keepalive消息将迁移至established状态,如果收到notification消息,将断开TCP连接,并且迁移至idle状态.6.

established

BGP完全建立连接,对等体之间相互交换update,keepalive,notification

消息.如果收到update或是keepalive

消息,则重新启动保持定时器(保持时间不为0);如果接收到的是notification消息,则迁移至idle状态.BGP

Established

and

Idle

StatesIdle:

The

router

in

this

state

cannot

find

the

addressof

the

neighbor

in

the

routing

table.Check

foranIGP

problem.

Is

the

neighbor

announcing

the

route?Established:

The

established

state

is

the

proper

state

for

BGP

operations.

In

the

output

of

the

showip

bgp

summary

command,

if

the

state

column

has

anumber,

then

the

route

is

in

the

established

state.The

number

is

how

many

routes

have

been

learnedfrom

this

neighbor.RouterA#sh

ip

bgp

neighborsBGP

neighbor

is

172.31.1.3, remote

AS

64998,

external

linkBGP

version

4,

remote

router

ID

172.31.2.3BGP

state=

Established,

up

for

00:19:10Last

readinterval

is00:00:10,

last

write

00:00:10,

hold

time

is

180,60

secondskeepaliveNeighbor

capabilities:Route

refresh:

advertised

and

received(old

&

new)Address

family

IPv4

Unicast:

advertised

and

receivedMessage

statistics:InQ

depth

is0OutQ

depth

is

0SentRcvdOpens:77Notifications:00Updates:1338<output

omitted>Example:

show

ip

bgp

neighborsCommandBGP

Active

State

TroubleshootingActive:

The

router

has

sent

an

open

packet

and

iswaiting

for

a

response.

The

state

may

cycle

betweenactive

and

idle.

The

neighbor

may

not

know

how

toget

back

to

this

router

because

of

the

followingreasons:Neighbor

does

not

have

a

route

to

the

source

IP

addressof

the

BGP

open

packet

generated

by

this

router.Neighbor

is

peering

with

the

wrong

address.Neighbor

does

not

have

a

neighbor

statement

for

thisrouter.AS

number

is

misconfiguration.Example:

BGP

Active

StateTroubleshootingAS

number

misconfiguration:At

the

router

with

the

wrong

remote

AS

number:%BGP-3-NOTIFICATION:

sent

to

neighbor172.31.1.3

2/2

(peer

inwrong

AS)

2

bytes

FDE6FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF002D0104FDE600B4AC1F02031002060104000100010202800002020200At

the

remote

router:%BGP-3-NOTIFICATION:

received

from

neighbor172.31.1.1

2/2

(peer

inwrong

AS)

2

bytes

FDE6Example:

BGP

PeeringRouterA#

show

ip

bgp

summaryBGP

router

identifier

10.1.1.1,

local

AS

number

65001BGP

table

version

is

124,

main

routing

table

version

1249

network

entries

using

1053

bytes

of

memory22

path

entries

using

1144

bytes

of

memory12/5

BGP

path/bestpath

attribute

entries

using

1488

bytes

of

memory6

BGP

AS-PATH

entries

using

144

bytes

of

memory0

BGP

route-map

cache

entries

using

0

bytes

of

memory0

BGP

filter-list

cache

entries

using

0

bytes

of

memoryBGP

using

3829

total

bytes

of

memoryBGP

activity

58/49

prefixes,

72/50

paths,

scan

interval

60

secsNeighbor

V AS

MsgRcvd

MsgSent

TblVer InQ

OutQ

Up/Down

State/PfxRcd10.1.0.246500111111240000:02:288172.31.1.346499821181240000:01:136172.31.11.446499911101240000:01:116BGP

NeighborAuthenticationBGP

authentication

uses

MD5.Configure

a

key

(password);

router

generates

amessage

digest,

or

hash,

of

the

key

and

the

message.Message

digest

is

sent;

key

is

not

sent.Router

generates

and

checks

the

MD5

digest

ofevery

segment

sent

on

the

TCP

connection.

Routerauthenticates

the

source

of

each

routing

updatepacket

that

it

receivesneighbor

{ip-address

|

peer-group-name}

password

stringRouter(config-router)#Example:

BGP

NeighborAuthenticationExample:

show

ip

bgp

CommandRouterA#

show

ip

bgpBGP

table

version

is

14,

local

router

ID

is

172.31.11.1Status

codes:

s

suppressed,

d

damped,

h

history,

*

valid,

>

best,

i

-internal,

r

RIB-failure,

S

StaleOrigin

codes:

i

-

IGP,

e

-

EGP,

?

-pleteMetric

LocPrf

Weight

Path1000000100Network*>

10.1.0.0/24*

i*>

10.1.1.0/24*>i10.1.2.0/24*>

10.97.97.0/24*100*

i*>

10.254.0.0/2400*10000100Next

Hop0.0.0.010.1.0.20.0.0.010.1.0.2172.31.1.3172.31.11.4172.31.11.4172.31.1.3172.31.11.4172.31.1.3172.31.1.3172.31.11.4172.31.1.3172.31.1.30032768

i0

i32768

i0

i0

64998

64997

i0

64999

64997

i0

64999

64997

i0

64998i0

64999

64998

i0

64998i0

64998i0

64999

64998

i0

64998i0

64998i*

ir>

172.31.1.0/24r

r

i*>

172.31.2.0/24<output

omitted>Displaysnetworks

from

lowesttohighestExample:

show

ip

bgp

rib-failureCommandRouterA#

showipbgp

rib-failureNetworkNext

HopRIB-failureRIB-NHMatches172.31.1.0/24172.31.1.3Higher

admin

distancen/a172.31.11.0/24172.31.11.4Higher

admin

distancen/aDisplays

networks

that

are

not

installed

in

the

RIB

and

the

reason

thatthey

were

not

installedClearing

the

BGPSessionWhen

policies

such

as

access

lists

or

attributes

arechanged,

the

change

takes

effect

immediately,

andthe

next

time

that

a

prefix

or

path

is

advertised

orreceived,

the

new

policy

is

used.

It

can

take

a

longtime

for

the

policy

to

be

applied

to

all

networks.You

must

trigger

an

update

to

ensure

that

the

policyis

immediately

applied

to

all

affected

prefixes

andpaths.Ways

to

trigger

an

update:Hard

resetSoftresetRoute

refreshclear

ip

bgp

*router#Hard

Reset

of

BGP

Sessionsclear

ip

bgp

[neighbor-address]Resets

all

BGP

connections

with

thisrouter.Entire

BGP

forwarding

table

is

discarded.BGP

session

makes

the

transition

from

established

to

idle;

everythingmust

berelearned.router#Resets

only

a

single

neighbor.BGP

session

makes

the

transition

from

established

to

idle;everything

from

this

neighbor

must

berelearned.Less

severe

than

clear

ip

bgp

*.Soft

Reset

Outboundclear

ip

bgp

{*|neighbor-address}

[soft

out]Router#Routes

learned

from

this

neighbor

are

not

lost.This

router

resends

all

BGP

information

to

the

neighbor

withoutresetting

theconnection.Theconnection

remains

established.This

option

is

highly mended

whenyou

are

changingoutboundpolicy.The

soft

out

option

does

not

help

if

you

are

changing

inboundpolicy.Inbound

Soft

Resetneighbor

[ip-address]

soft-reconfiguration

inboundRouter(config-router)#clear

ip

bgp

{*|neighbor-address}

soft

inThis

router

stores

all

updates

from

this

neighbor

in

case

theinboundpolicy

is

changed.The

command

is

memory-intensive.Router#Uses

the

stored

information

to

generate

new

inboundupdatesclear

ip

bgp

{*|neighbor-address}

[soft

in

|

in]Router#Routes

advertised

to

this

neighbor

are

not

withdrawn.Does

not

store

update

information

locally.Theconnection

remains

established.Introduced

in

Cisco

IOS

software

release

12.0(2)S

and12.0(6)T.Route

Refresh:

Dynamic

InboundSoft

Resetdebug

ip

bgp

updates

CommandRouterA#debug

ip

bgp

updatesMobile

router

debugging

is

on

for

address

family