Are you ready to find prefixes that go bump in the night?Here is the sample Trouble Ticket we will attack , and the appropriate portion of the Cisco diagram .You will want to have so mescratch paper handy(just like in the actual exam).Diagramming can prove to be more important here then in any exam section.You should practice a diagram now based on the show output that follows.

TroubleTicket1

VampireslocatedinVLAN666(behindAmityville)areunabletoaccessanyresourceslocatedbehindTransylvania.Correctthisissuewithoutstaticrouting,additionalroutingprotocols,orredistributionofanykind.

Thefirstorderofbusinessisto“expand”upontheirdiagramanddeterminewhatprotocolsareinuseandwhere.Aquickshowipprotocolsoneachofthedevicesinthetransitpathshoulddothetrick.

Transylvania#showipprotocols

RoutingProtocolis"eigrp100"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

Defaultnetworksflaggedinoutgoingupdates

Defaultnetworksacceptedfromincomingupdates

EIGRPmetricweightK1=1,K2=0,K3=1,K4=0,K5=0

EIGRPmaximumhopcount100

EIGRPmaximummetricvariance1

Redistributing:eigrp100

EIGRPNSF-awarerouteholdtimeris240s

Automaticnetworksummarizationisnotineffect

Maximumpath:4

RoutingforNetworks:

53.234.10.23/32

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:internal90external170

RoutingProtocolis"bgp65001"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

IGPsynchronizationisdisabled

Automaticroutesummarizationisdisabled

UnicastAggregateGeneration:

10.10.0.0/16summary-only

Neighbor(s):

AddressFiltInFiltOutDistInDistOutWeightRouteMap

53.234.10.44

Maximumpath:1

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:external20internal200local200

HalloweenTown#showipprotocols

RoutingProtocolis"eigrp100"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

Defaultnetworksflaggedinoutgoingupdates

Defaultnetworksacceptedfromincomingupdates

EIGRPmetricweightK1=1,K2=0,K3=1,K4=0,K5=0

EIGRPmaximumhopcount100

EIGRPmaximummetricvariance1

Redistributing:eigrp100

EIGRPNSF-awarerouteholdtimeris240s

Automaticnetworksummarizationisnotineffect

Maximumpath:4

RoutingforNetworks:

53.234.10.44/32

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:internal90external170

RoutingProtocolis"bgp65001"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

IGPsynchronizationisdisabled

Automaticroutesummarizationisdisabled

Neighbor(s):

AddressFiltInFiltOutDistInDistOutWeightRouteMap

23.10.24.190

53.234.10.23

Maximumpath:1

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:external20internal200local200

Salem#showipprotocols

RoutingProtocolis"ospf1"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

RouterID66.150.201.12

Numberofareasinthisrouteris1.1normal0stub0nssa

Maximumpath:4

RoutingforNetworks:

RoutingonInterfacesConfiguredExplicitly(Area0):

FastEthernet0/0

Referencebandwidthunitis100mbps

RoutingInformationSources:

GatewayDistanceLastUpdate

102.34.102.1211000:30:55

Distance:(defaultis110)

RoutingProtocolis"bgp65000"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

IGPsynchronizationisdisabled

Automaticroutesummarizationisdisabled

Neighbor(s):

AddressFiltInFiltOutDistInDistOutWeightRouteMap

23.10.24.200

Maximumpath:1

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:external20internal200local200

CrystalLake#showipprotocols

RoutingProtocolis"ospf1"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

RouterID102.34.102.1

Numberofareasinthisrouteris1.1normal0stub0nssa

Maximumpath:4

RoutingforNetworks:

RoutingonInterfacesConfiguredExplicitly(Area0):

FastEthernet0/1

FastEthernet0/0

Referencebandwidthunitis100mbps

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:(defaultis110)

RoutingProtocolis"bgp65000"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

IGPsynchronizationisdisabled

Automaticroutesummarizationisdisabled

Neighbor(s):

AddressFiltInFiltOutDistInDistOutWeightRouteMap

66.150.201.12

AddressFiltInFiltOutDistInDistOutWeightRouteMap

102.34.102.12

Maximumpath:1

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:external20internal200local200

Amityville#showipprotocols

RoutingProtocolis"ospf1"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

RouterID102.34.102.12

Numberofareasinthisrouteris1.1normal0stub0nssa

Maximumpath:4

RoutingforNetworks:

RoutingonInterfacesConfiguredExplicitly(Area0):

FastEthernet0/0

Referencebandwidthunitis100mbps

RoutingInformationSources:

GatewayDistanceLastUpdate

102.34.102.111000:33:23

Distance:(defaultis110)

RoutingProtocolis"bgp65000"

Outgoingupdatefilterlistforallinterfacesisnotset

Incomingupdatefilterlistforallinterfacesisnotset

IGPsynchronizationisdisabled

Automaticroutesummarizationisdisabled

Neighbor(s):

AddressFiltInFiltOutDistInDistOutWeightRouteMap

102.34.102.1

Maximumpath:1

RoutingInformationSources:

GatewayDistanceLastUpdate

Distance:external20internal200local200AsIparsetheresults,Icreateamoredetaileddiagramtoprovideabetterpictureofwhatisgoingon.Lookingatthediagram,Iimmediatelycontemplatesomedesignissuesthatcouldcomeintoplay.TheiBGPsplit-horizonrule,next-hopreachability,andsynchronizationallcouldcomeintoplayheregiventheprotocolconfiguration.

Idecidetostartasclosethedestinationaspossibleandexaminetherelevantconfigurations.

Transylvania#showrun|sectionbgp

routerbgp65001

nosynchronization

bgplog-neighbor-changes

network10.0.0.0

aggregate-address10.10.0.0255.255.0.0summary-only

neighbor53.234.10.44remote-as65001

noauto-summaryItappearstheintentistoadvertiseprefixes(theLoopbackinterfaces)beyondTransylvaniausingBGPprefixaggregation.Letmeensurethatconfigurationisdonecorrectly.

Sureenough,hereisourfirstBGPconfigurationissue.Weneedtoadvertiseacomponentprefixoftheaggregate.Thelittlegremlinthatattemptedthisconfigurationtriedtoaccomplishthiswiththenetworkstatement,buttheygotitwrong.Subnettingisbeingdonehereofthe10.x.x.xspace,soyouneedtoreconfigurethenetworkstatementasfollows:

Transylvania#showipintbrief

InterfaceIP-AddressOK?MethodStatusProtocol

FastEthernet0/053.234.10.23YESmanualupup

FastEthernet0/1unassignedYESunsetadministrativelydowndown

Loopback110.10.10.1YESmanualupup

Loopback210.10.11.1YESmanualupup

Loopback310.10.12.1YESmanualupup

Transylvania#configureterminal

Enterconfigurationcommands,oneperline.EndwithCNTL/Z.

Transylvania(config)#routerbgp65001

Transylvania(config-router)#network10.10.10.0mask255.255.255.0

Aftermakingthischange,IcheckSalemtoseeifitisreceivingtheaggregatefromTransylvaniaandwehavereachability:

Salem#showipbgp

BGPtableversionis2,localrouterIDis66.150.201.12

Statuscodes:ssuppressed,ddamped,hhistory,*valid,>best,i-internal,

rRIB-failure,SStale

Origincodes:i-IGP,e-EGP,?-incomplete

NetworkNextHopMetricLocPrfWeightPath

*>10.10.0.0/1623.10.24.200065001i

Salem#showiproutebgp

10.0.0.0/16issubnetted,1subnets

B10.10.0.0[20/0]via23.10.24.200,00:06:26

Salem#ping10.10.10.1

Typeescapesequencetoabort.

Sending5,100-byteICMPEchosto10.10.10.1,timeoutis2seconds:

!!!!!

Successrateis100percent(5/5),round-tripmin/avg/max=28/33/40msWeareonourwaytosolvingthisTroubleTicket…wehopeyouwillfollowthisblogandcontinuethis(andmore)troubleshootingscenarios!

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