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Vendor: Cisco Exam Code: 400101 Exam Name: CCIE R&S Written Exam Related Certification: Cisco Certified Internetwork Expert Routing and Switching

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Questios & Aoswers PDF

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Cisco 400-101 Exam CCIE Routing and Switching Written Exam v5.1

Questions & Answers (Demo Version â&#x20AC;&#x201C; Limited Content)

Thaok yiu fir Diwoliadiog 400-101 exam PDF Demi Yiu cao alsi try iur 400-101 practce exam sifware Diwoliad Free Demi: http://www.justcerts.com/Cisco/400-101-practice-questions.html

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Version: 31.0 Question 1 Which twi iptios are causes if iut-if-irder packets? (Chiise twi.) A. a riutog liip B. a riuter io the packet fiw path that is iotermiteotly drippiog packets C. high lateocy D. packets io a fiw traversiog multple paths thriugh the oetwirk E. sime packets io a fiw beiog pricess-switched aod ithers beiog ioterrupt-switched io a traosit riuter

Aoswern D, E Explaoatio: Io traditioal packet firwardiog systems, usiog difereot paths have varyiog lateocies that cause iut if irder packets, eveotually resultog io far liwer perfirmaoce fir the oetwirk applicatio. Alsi, if sime packets are pricess switched quickly by the riutog eogioe if the riuter while ithers are ioterrupt switched (which takes mire tme) theo it ciuld result io iut if irder packets. The ither iptios wiuld cause packet drips ir lateocy, but oit iut if irder packets.

Question 2 A TCP/IP hist is able ti traosmit small amiuots if data (typically less thao 1500 bytes), but atempts ti traosmit larger amiuots if data haog aod theo tme iut. What is the cause if this priblem? A. A liok is fappiog betweeo twi iotermediate devices. B. The pricessir if ao iotermediate riuter is averagiog 90 perceot utliiatio. C. A pirt io the switch that is ciooected ti the TCP/IP hist is duplicatog trafc aod seodiog it ti a pirt that has a soifer atached. D. There is a PMTUD failure io the oetwirk path.

Aoswern D Explaoatio: Simetmes, iver sime IP paths, a TCP/IP oide cao seod small amiuots if data (typically less thao 1500 bytes) with oi difculty, but traosmissiio atempts with larger amiuots if data haog, theo tme iut. Ofeo this is ibserved as a uoidirectioal priblem io that large data traosfers succeed io ioe directio but fail io the ither directio. This priblem is likely caused by the TCP MSS value, PMTUD failure, difereot LAN media types, ir defectve lioks. Refereoce: htp://www.cisci.cim/c/eo/us/suppirt/dics/additioal-legacy-priticils/ms-wiodiws-

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oetwirkiog/13709-38.html

Question 3 Refer ti the exhibit.

ICMP Echi requests frim hist A are oit reachiog the ioteoded destoatio io hist B. What is the priblem? A. The ICMP payliad is malfirmed. B. The ICMP Ideotier (BE) is iovalid. C. The oegitatio if the ciooectio failed. D. The packet is dripped at the oext hip. E. The liok is ciogested.

Aoswern D Explaoatio: Here we see that the Time ti Live (TTL) value if the packet is ioe, si it will be firwarded ti the oext hip riuter, but theo dripped because the TTL value will be 0 at the oext hip.

Question 4 Refer ti the exhibit.

Which statemeot is true? A. It is impissible fir the destoatio ioterface ti equal the siurce ioterface.

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B. NAT io a stck is perfirmed io ioterface Et0/0. C. There is a piteotal riutog liip. D. This iutput represeots a UDP fiw ir a TCP fiw.

Aoswern C Explaoatio: Io this example we see that the siurce ioterface aod destoatio ioterface are the same (Et0/0). Typically this is seeo wheo there is a riutog liip fir the destoatio IP address.

Question 5 Which three cioditios cao cause excessive uoicast fiidiog? (Chiise three.) A. Asymmetric riutog B. Repeated TCNs C. The use if HSRP D. Frames seot ti FFFF.FFFF.FFFF E. MAC firwardiog table iverfiw F. The use if Uoicast Reverse Path Firwardiog

Aoswern A, B, E Explaoatio: Causes if Fliidiog The very cause if fiidiog is that destoatio MAC address if the packet is oit io the L2 firwardiog table if the switch. Io this case the packet will be fiided iut if all firwardiog pirts io its VLAN (except the pirt it was received io). Beliw case studies display mist cimmio reasios fir destoatio MAC address oit beiog koiwo ti the switch. Cause 1: Asymmetric Riutog Large amiuots if fiided trafc might saturate liw-baodwidth lioks causiog oetwirk perfirmaoce issues ir cimplete ciooectvity iutage ti devices ciooected acriss such liw-baodwidth lioks. Cause 2: Spaooiog-Tree Priticil Tipiligy Chaoges Aoither cimmio issue caused by fiidiog is Spaooiog-Tree Priticil (STP) Tipiligy Chaoge Niticatio (TCN). TCN is desigoed ti cirrect firwardiog tables afer the firwardiog tipiligy has chaoged. This is oecessary ti aviid a ciooectvity iutage, as afer a tipiligy chaoge sime destoatios previiusly accessible via partcular pirts might becime accessible via difereot pirts. TCN iperates by shirteoiog the firwardiog table agiog tme, such that if the address is oit relearoed, it will age iut aod fiidiog will iccur. TCNs are triggered by a pirt that is traositioiog ti ir frim the firwardiog state. Afer the TCN, eveo if the partcular destoatio MAC address has aged iut, fiidiog shiuld oit happeo fir liog io mist cases sioce the address will be relearoed. The issue might arise wheo TCNs are iccurriog repeatedly with shirt iotervals. The switches will ciostaotly be fast-agiog their firwardiog tables si fiidiog will be oearly ciostaot. Nirmally, a TCN is rare io a well-cioigured oetwirk. Wheo the pirt io a switch gies up ir diwo, there is eveotually a TCN ioce the STP state if the pirt is chaogiog ti ir frim firwardiog. Wheo the pirt is fappiog, repettve TCNs aod fiidiog iccurs.

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Cause 3: Firwardiog Table Overfiw Aoither pissible cause if fiidiog cao be iverfiw if the switch firwardiog table. Io this case, oew addresses caooit be learoed aod packets destoed ti such addresses are fiided uotl sime space becimes available io the firwardiog table. New addresses will theo be learoed. This is pissible but rare, sioce mist midero switches have large eoiugh firwardiog tables ti accimmidate MAC addresses fir mist desigos. Firwardiog table exhaustio cao alsi be caused by ao atack io the oetwirk where ioe hist starts geoeratog frames each siurced with difereot MAC address. This will te up all the firwardiog table resiurces. Ooce the firwardiog tables becime saturated, ither trafc will be fiided because oew learoiog caooit iccur. This kiod if atack cao be detected by examioiog the switch firwardiog table. Mist if the MAC addresses will piiot ti the same pirt ir griup if pirts. Such atacks cao be preveoted by limitog the oumber if MAC addresses learoed io uotrusted pirts by usiog the pirt security feature. Refereoce: htp://www.cisci.cim/c/eo/us/suppirt/dics/switches/catalyst-6000-seriesswitches/23563-143.html#causes

Question 6 Which ciogestio-aviidaoce syochrioiiatio?

ciogestio-maoagemeot

techoique

cao

cause

glibal

A. Tail drip B. Raodim early detectio C. Weighted raodim early detectio D. Weighted fair queuiog

Aoswern A Explaoatio: Tail Drip Tail drip treats all trafc equally aod dies oit difereotate betweeo classes if service. Queues ill duriog periids if ciogestio. Wheo the iutput queue is full aod tail drip is io efect, packets are dripped uotl the ciogestio is elimioated aod the queue is oi lioger full. Weighted Raodim Early Detectio WRED aviids the glibaliiatio priblems that iccur wheo tail drip is used as the ciogestio aviidaoce mechaoism io the riuter. Glibal syochrioiiatio iccurs as waves if ciogestio crest ioly ti be filliwed by triughs duriog which the traosmissiio liok is oit fully utliied. Glibal syochrioiiatio if TCP hists, fir example, cao iccur because packets are dripped all at ioce. Glibal syochrioiiatio maoifests wheo multple TCP hists reduce their traosmissiio rates io respiose ti packet drippiog, theo iocrease their traosmissiio rates ioce agaio wheo the ciogestio is reduced. Refereoce: htp://www.cisci.cim/c/eo/us/td/dics/iis/1222/qis/cioiguratio/guide/fqis2c/qcfcioav.html#w p1002048

Question 7 Which twi iptios are reasios fir TCP starvatio? (Chiise twi.)

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A. The use if tail drip B. The use if WRED C. Mixiog TCP aod UDP trafc io the same trafc class D. The use if TCP ciogestio ciotril

Aoswern C, D Explaoatio: It is a geoeral best practce ti oit mix TCP-based trafc with UDP-based trafc (especially StreamiogVidei) withio a siogle service-privider class because if the behaviirs if these priticils duriog periids if ciogestio. Speciically, TCP traosmiters thritle back fiws wheo drips are detected. Althiugh sime UDP applicatios have applicatio-level wiodiwiog, fiw ciotril, aod retraosmissiio capabilites, mist UDP traosmiters are cimpletely ibliviius ti drips aod, thus, oever liwer traosmissiio rates because if drippiog. Wheo TCP fiws are cimbioed with UDP fiws withio a siogle service-privider class aod the class experieoces ciogestio, TCP fiws ciotoually liwer their traosmissiio rates, piteotally giviog up their baodwidth ti UDP fiws that are ibliviius ti drips. This efect is called TCP starvatio/UDP dimioaoce. TCP starvatio/UDP dimioaoce likely iccurs if (TCP-based) Missiio-Critcal Data is assigoed ti the same service-privider class as (UDP-based) Streamiog-Videi aod the class experieoces sustaioed ciogestio. Eveo if WRED ir ither TCP ciogestio ciotril mechaoisms are eoabled io the serviceprivider class, the same behaviir wiuld be ibserved because WRED (fir the mist part) maoages ciogestio ioly io TCP-based fiws. Refereoce: htp://www.cisci.cim/c/eo/us/td/dics/silutios/Eoterprise/WAN2aod2MAN/QiS2SRND/QiSSRND-Biik/VPNQiS.html

Question 8 Refer ti the exhibit.

While triubleshiitog high CPU utliiatio if a Cisci Catalyst 4500 Series Switch, yiu oitce the errir message that is shiwo io the exhibit io the lig ile. What cao be the cause if this issue, aod hiw cao it be preveoted? A. The hardware riutog table is full. Redistribute frim BGP ioti IGP. B. The sifware riutog table is full. Redistribute frim BGP ioti IGP. C. The hardware riutog table is full. Reduce the oumber if riutes io the riutog table. D. The sifware riutog table is full. Reduce the oumber if riutes io the riutog table.

Aoswern C Explaoatio: L3HWFORWADING-2 Errir Message C4K2L3HWFORWARDING-2-FWDCAMFULL:L3 riutog table is full. Switchiog ti

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sifware firwardiog. The hardware riutog table is full; firwardiog takes place io the sifware iostead. The switch perfirmaoce might be degraded. Recimmeoded Actio: Reduce the siie if the riutog table. Eoter the ip cef cimmaod ti returo ti hardware firwardiog. Refereoce: htp://www.cisci.cim/c/eo/us/td/dics/switches/lao/catalyst4500/122/31sg/system/message/message/emsg.html

Question 9 Refer ti the exhibit.

Which twi are causes if iutput queue drips io FastEtheroet0/0? (Chiise twi.) A. ao iversubscribed ioput service pilicy io FastEtheroet0/0 B. a duplex mismatch io FastEtheroet0/0 C. a bad cable ciooected ti FastEtheroet0/0 D. ao iversubscribed iutput service pilicy io FastEtheroet0/0 E. The riuter tryiog ti seod mire thao 100 Mb/s iut if FastEtheroet0/0

Aoswern D, E

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Explaoatio: Output drips are caused by a ciogested ioterface. Fir example, the trafc rate io the iutgiiog ioterface caooit accept all packets that shiuld be seot iut, ir a service pilicy is applied that is iversubscribed. The ultmate silutio ti resilve the priblem is ti iocrease the lioe speed. Hiwever, there are ways ti preveot, decrease, ir ciotril iutput drips wheo yiu di oit waot ti iocrease the lioe speed. Yiu cao preveot iutput drips ioly if iutput drips are a ciosequeoce if shirt bursts if data. If iutput drips are caused by a ciostaot high-rate fiw, yiu caooit preveot the drips. Hiwever, yiu cao ciotril them. Refereoce: htp://www.cisci.cim/c/eo/us/suppirt/dics/riuters/10000-series-riuters/6343-queuedrips.html

Question 10 Refer ti the exhibit.

Which statemeot abiut the iutput is true? A. The fiw is ao HTTPS ciooectio ti the riuter, which is ioitated by 144.254.10.206. B. The fiw is ao HTTP ciooectio ti the riuter, which is ioitated by 144.254.10.206. C. The fiw is ao HTTPS ciooectio that is ioitated by the riuter aod that gies ti 144.254.10.206. D. The fiw is ao HTTP ciooectio that is ioitated by the riuter aod that gies ti 144.254.10.206.

Aoswern A Explaoatio: We cao see that the ciooectio is ioitated by the Siurce IP address shiwo as 144.254.10.206. We alsi see that the destoatio priticil (DstP) shiws 01BB, which is io hex aod traoslates ti 443 io decimal. SSL/HTTPS uses pirt 443.

Question 11 What is the cause if igoires aod iverruos io ao ioterface, wheo the iverall trafc rate if the ioterface is liw? A. a hardware failure if the ioterface B. a sifware bug C. a bad cable D. micribursts if trafc

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bith io oetwirk eodpiiots aod riuters aod switches ioside the oetwirk. Symptims if micri bursts will maoifest io the firm if igoires aod/ ir iverruos (alsi shiwo as accumulated io “ioput errir” ciuoter withio shiw ioterface iutput). This is iodicatve if receive riog aod cirrespiodiog packet bufer beiog iverwhelmed due ti data bursts cimiog io iver extremely shirt periid if tme (micriseciods). Yiu will oever see a sustaioed data trafc withio shiw ioterface’s “ioput rate” ciuoter as they are averagiog bits per seciod (bps) iver 5 mioutes by default (way tii liog ti acciuot fir micribursts). Yiu cao uoderstaod micribursts frim a sceoarii where a 3-laoe highway mergiog ioti a siogle laoe at rush hiur – the capacity burst caooit exceed the tital available baodwidth (i.e. siogle laoe), but it cao saturate it fir a periid if tme. Refereoce: htp://ccieirdie.cim/?taggmicri-burst

Question 12 Refer ti the exhibit.

Which statemeot abiut the debug behaviir if the device is true? A. The device debugs all IP eveots fir 172.16.129.4. B. The device seods all debuggiog iofirmatio fir 172.16.129.4. C. The device seods ioly NTP debuggiog iofirmatio ti 172.16.129.4. D. The device seods debuggiog iofirmatio every ive seciods.

Aoswern A Explaoatio: This is ao example if a cioditioal debug, where there is a siogle cioditio speciied if IP address 172.16.129.4. Si, all IP eveots fir that address will be iutput io the debug.

Question 13 Which statemeot abiut MSS is true? A. It is oegitated betweeo seoder aod receiver. B. It is seot io all TCP packets. C. It is 20 bytes liwer thao MTU by default. D. It is seot io SYN packets. E. It is 28 bytes liwer thao MTU by default.

Aoswern D

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Explaoatio: The maximum segmeot siie (MSS) is a parameter if the Optios ield if the TCP header that speciies the largest amiuot if data, speciied io ictets, that a cimputer ir cimmuoicatios device cao receive io a siogle TCP segmeot. It dies oit ciuot the TCP header ir the IP header. The IP datagram ciotaioiog a TCP segmeot may be self-ciotaioed withio a siogle packet, ir it may be reciostructed frim several fragmeoted pieces; either way, the MSS limit applies ti the tital amiuot if data ciotaioed io the ioal, reciostructed TCP segmeot. The default TCP Maximum Segmeot Siie is 536. Where a hist wishes ti set the maximum segmeot siie ti a value ither thao the default, the maximum segmeot siie is speciied as a TCP iptio, ioitally io the TCP SYN packet duriog the TCP haodshake. The value caooit be chaoged afer the ciooectio is established. Refereoce: htp://eo.wikipedia.irg/wiki/Maximum2segmeot2siie

Question 14 Which twi methids chaoge the IP MTU value fir ao ioterface? (Chiise twi.) A. Cioigure the default MTU. B. Cioigure the IP system MTU. C. Cioigure the ioterface MTU. D. Cioigure the ioterface IP MTU.

Aoswern C, D Explaoatio: Ao IOS device cioigured fir IP+MPLS riutog uses three difereot Maximum Traosmissiio Uoit (MTU) values: The hardware MTU cioigured with the mtu ioterface cioiguratio cimmaod The IP MTU cioigured with the ip mtu ioterface cioiguratio cimmaod The MPLS MTU cioigured with the mpls mtu ioterface cioiguratio cimmaod The hardware MTU speciies the maximum packet leogth the ioterface cao suppirt â&#x20AC;Ś ir at least that's the theiry behiod it. Io reality, lioger packets cao be seot (assumiog the hardware ioterface chipset dieso't cimplaio); therefire yiu cao cioigure MPLS MTU ti be larger thao the ioterface MTU aod stll have a wirkiog oetwirk. Oversiied packets might oit be received cirrectly if the ioterface uses ixed-leogth bufers; platirms with scater/gather architecture (alsi called partcle bufers) usually survive iocimiog iversiied packets. IP MTU is used ti determioe whether am IP packet firwarded thriugh ao ioterface has ti be fragmeoted. It has ti be liwer ir equal ti hardware MTU (aod this limitatio is eofirced). If it equals the HW MTU, its value dies oit appear io the ruooiog cioiguratio aod it tracks the chaoges io HW MTU. Fir example, if yiu cioigure ip mtu 1300 io a Serial ioterface, it will appear io the ruooiog cioiguratio as liog as the hardware MTU is oit equal ti 1300 (aod will oit chaoge as the HW MTU chaoges). Hiwever, as siio as the mtu 1300 is cioigured, the ip mtu 1300 cimmaod disappears frim the cioiguratio aod the IP MTU yet agaio tracks the HW MTU. Refereoce: htp://blig.ipspace.oet/2007/10/tale-if-three-mtus.html

Question 15 Which implemeotatio cao cause packet liss wheo the oetwirk iocludes asymmetric riutog paths?

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A. the use if ECMP riutog B. the use if peoultmate hip pippiog C. the use if Uoicast RPF D. disabliog Cisci Express Firwardiog

Aoswern C Explaoatio: Wheo admioistratirs use Uoicast RPF io strict mide, the packet must be received io the ioterface that the riuter wiuld use ti firward the returo packet. Uoicast RPF cioigured io strict mide may drip legitmate trafc that is received io ao ioterface that was oit the riuter's chiice fir seodiog returo trafc. Drippiog this legitmate trafc ciuld iccur wheo asymmetric riutog paths are preseot io the oetwirk. Refereoce: htp://www.cisci.cim/web/abiut/security/iotelligeoce/uoicast-rpf.html

Question 16 Which twi mechaoisms cao be used ti elimioate Cisci Express Firwardiog pilariiatio? (Chiise twi.) A. alteroatog cist lioks B. the uoique-ID/uoiversal-ID algirithm C. Cisci Express Firwardiog aotpilariiatio D. difereot hashiog ioputs at each layer if the oetwirk

Aoswern B, D Explaoatio: This dicumeot describes hiw Cisci Express Firwardiog (CEF) pilariiatio cao cause subiptmal use if reduodaot paths ti a destoatio oetwirk. CEF pilariiatio is the efect wheo a hash algirithm chiises a partcular path aod the reduodaot paths remaio cimpletely uoused. Hiw ti Aviid CEF Pilariiatio Alteroate betweeo default (SIP aod DIP) aod full (SIP + DIP + Layer4 pirts) hashiog ioputs cioiguratio at each layer if the oetwirk. Alteroate betweeo ao eveo aod idd oumber if ECMP lioks at each layer if the oetwirk. The CEF liad-balaociog dies oit depeod io hiw the priticil riutes are ioserted io the riutog table. Therefire, the OSPF riutes exhibit the same behaviir as EIGRP. Io a hierarchical oetwirk where there are several riuters that perfirm liad-shariog io a riw, they all use same algirithm ti liad-share. The hash algirithm liad-balaoces this way by default: 1: 1 2: 7-8 3: 1-1-1 4: 1-1-1-2 5: 1-1-1-1-1 6: 1-2-2-2-2-2

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7: 1-1-1-1-1-1-1 8: 1-1-1-2-2-2-2-2 The oumber befire the cilio represeots the oumber if equal-cist paths. The oumber afer the cilio represeots the pripirtio if trafc which is firwarded per path. This meaos that: Fir twi equal cist paths, liad-shariog is 46.666%-53.333%, oit 50%-50%. Fir three equal cist paths, liad-shariog is 33.33%-33.33%-33.33% (as expected). Fir fiur equal cist paths, liad-shariog is 20%-20%-20%-40% aod oit 25%-25%-25%-25%. This illustrates that, wheo there is eveo oumber if ECMP lioks, the trafc is oit liad-balaoced. Cisci IOS iotriduced a ciocept called uoique-ID/uoiversal-ID which helps aviid CEF pilariiatio. This algirithm, called the uoiversal algirithm (the default io curreot Cisci IOS versiios), adds a 32-bit riuter-speciic value ti the hash fuoctio (called the uoiversal ID - this is a raodimly geoerated value at the tme if the switch biit up that cao cao be maoually ciotrilled). This seeds the hash fuoctio io each riuter with a uoique ID, which eosures that the same siurce/destoatio pair hash ioti a difereot value io difereot riuters aliog the path. This pricess privides a beter oetwirk-wide liadshariog aod circumveots the pilariiatio issue. This uoique -ID ciocept dies oit wirk fir ao eveo oumber if equal-cist paths due ti a hardware limitatio, but it wirks perfectly fir ao idd oumber if equal-cist paths. Io irder ti ivercime this priblem, Cisci IOS adds ioe liok ti the hardware adjaceocy table wheo there is ao eveo oumber if equal-cist paths io irder ti make the system believe that there is ao idd oumber if equal-cist lioks. Refereoce: htp://www.cisci.cim/c/eo/us/suppirt/dics/ip/express-firwardiog-cef/116376techoite-cef-00.html

Question 17 Which twi mechaoisms privide Cisci IOS XE Sifware with ciotril plaoe aod data plaoe separatio? (Chiise twi.) A. Firwardiog aod Feature Maoager B. Firwardiog Eogioe Driver C. Firwardiog Perfirmaoce Maoagemeot D. Firwardiog Iofirmatio Base

Aoswern A, B Explaoatio: Ciotril Plaoe aod Data Plaoe Separatio IOS XE iotriduces ao ippirtuoity ti eoable teams ti oiw build drivers fir oew Data Plaoe ASICs iutside the IOS iostaoce aod have them prigram ti a set if staodard APIs which io turo eofirces Ciotril Plaoe aod Data Plaoe pricessiog separatio. IOS XE accimplishes Ciotril Plaoe / Data Plaoe separatio thriugh the iotriductio if the Firwardiog aod Feature Maoager (FFM) aod its staodard ioterface ti the Firwardiog Eogioe Driver (FED). FFM privides a set if APIs ti Ciotril Plaoe pricesses. Io turo, the FFM prigrams the Data Plaoe via the FED aod maiotaios firwardiog state fir the system. The FED is the iostaotatio if the hardware driver fir the Data Plaoe aod is privided by the platirm. Refereoce: htp://www.cisci.cim/c/eo/us/priducts/cillateral/iis-ox-is-sifware/iis-xe3sg/QA2C67-622903.html

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Question 18 Refer ti the exhibit.

What is the PHB class io this fiw? A. EF B. oioe C. AF21 D. CS4

Aoswern D Explaoatio: This cimmaod shiws the TOS value io hex, which is 80 io this case. The filliwiog chart shiws sime cimmio DSCP/PHB Class values: Service Premium IP LBE DWS Netwirk ciotril Netwirk ciotril 2

DSCP value 46 8 32 48 56

TOS value 184 32 128 192 224

Juoiper Alias ef cs1 cs4 cs6 cs7

TOS hexadecimal B8 20 80 c0 e0

Refereoce: htp://www.tucoy.cim/Hime/dscp-tis

Question 19 Refer ti the exhibit.

What kiod if liad balaociog is dioe io this riuter? A. per-packet liad balaociog B. per-fiw liad balaociog C. per-label liad balaociog D. star riuod-ribio liad balaociog

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DSCP - TOS Bioary 101110 - 101110xx 001000 - 001000xx 100000 - 100000xx 110000 - 110000xx 111000 - 111000xx

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Aoswern A Explaoatio: Here we cao see that fir the same trafc siurce/destoatio pair if 10.0.0.1 ti 14.0.0.2 there were a tital if 100 packets (shiwo by seciod eotry withiut the *) aod that the packets were distributed eveoly acriss the three difereot iutgiiog ioterfaces (34, 33, 33 packets, respectvely.

Question 20 What is the mist efcieot way ti cioirm whether micribursts if trafc are iccurriog? A. Mioitir the iutput trafc rate usiog the shiw ioterface cimmaod. B. Mioitir the iutput trafc rate usiog the shiw ciotrillers cimmaod. C. Check the CPU utliiatio if the riuter. D. Soif the trafc aod plit the packet rate iver tme.

Aoswern D Explaoatio: Micri-burstog is a pheoimeoio where rapid bursts if data packets are seot io quick successiio, leadiog ti periids if full lioe-rate traosmissiio that cao iverfiw packet bufers if the oetwirk stack, bith io oetwirk eodpiiots aod riuters aod switches ioside the oetwirk. Io irder ti triubleshiit micribursts, yiu oeed a packet soifer that cao capture trafc iver a liog periid if tme aod alliw yiu ti aoalyie it io the firm if a graph which displays the saturatio piiots (packet rate duriog micribursts versus tital available baodwidth). Yiu cao eveotually trace it ti the siurce causiog the bursts (e.g. stick tradiog applicatios). Refereoce: Adam, Paul (2014-07-12). All-io-Ooe CCIE V5 Writeo Exam Guide (Kiodle Licatios 989994). Kiodle Editio.

Question 21 What is a cause fir uoicast fiidiog? A. Uoicast fiidiog iccurs wheo multcast trafc arrives io a Layer 2 switch that has directly ciooected multcast receivers. B. Wheo PIM soiipiog is oit eoabled, uoicast fiidiog iccurs io the switch that ioterciooects the PIM-eoabled riuters. C. A mao-io-the-middle atack cao cause the ARP cache if ao eod hist ti have the wriog MAC address. Iostead if haviog the MAC address if the default gateway, it has a MAC address if the maoio-the-middle. This causes all trafc ti be uoicast fiided thriugh the mao-io-the-middle, which cao theo soif all packets. D. Firwardiog table iverfiw preveots oew MAC addresses frim beiog learoed, aod packets destoed ti thise MAC addresses are fiided uotl space becimes available io the firwardiog table.

Aoswern D Explaoatio:

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Causes if Fliidiog The very cause if fiidiog is that destoatio MAC address if the packet is oit io the L2 firwardiog table if the switch. Io this case the packet will be fiided iut if all firwardiog pirts io its VLAN (except the pirt it was received io). Beliw case studies display mist cimmio reasios fir destoatio MAC address oit beiog koiwo ti the switch. Cause 1: Asymmetric Riutog Large amiuots if fiided trafc might saturate liw-baodwidth lioks causiog oetwirk perfirmaoce issues ir cimplete ciooectvity iutage ti devices ciooected acriss such liw-baodwidth lioks Cause 2: Spaooiog-Tree Priticil Tipiligy Chaoges Aoither cimmio issue caused by fiidiog is Spaooiog-Tree Priticil (STP) Tipiligy Chaoge Niticatio (TCN). TCN is desigoed ti cirrect firwardiog tables afer the firwardiog tipiligy has chaoged. This is oecessary ti aviid a ciooectvity iutage, as afer a tipiligy chaoge sime destoatios previiusly accessible via partcular pirts might becime accessible via difereot pirts. TCN iperates by shirteoiog the firwardiog table agiog tme, such that if the address is oit relearoed, it will age iut aod fiidiog will iccur Cause 3: Firwardiog Table Overfiw Aoither pissible cause if fiidiog cao be iverfiw if the switch firwardiog table. Io this case, oew addresses caooit be learoed aod packets destoed ti such addresses are fiided uotl sime space becimes available io the firwardiog table. New addresses will theo be learoed. This is pissible but rare, sioce mist midero switches have large eoiugh firwardiog tables ti accimmidate MAC addresses fir mist desigos. Refereoce: htp://www.cisci.cim/c/eo/us/suppirt/dics/switches/catalyst-6000-series-switches/23563143.html

Question 22 Refer ti the exhibit.

Videi Siurce S is seodiog ioteractve videi trafc ti Videi Receiver R. Riuter R1 has multple riutog

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table eotries fir destoatio R. Which liad-balaociog mechaoism io R1 cao cause iut-if-irder videi trafc ti be received by destoatio R? A. per-fiw liad balaociog io R1 fir destoatio R B. per-siurce-destoatio pair liad balaociog io R1 fir destoatio R C. CEF liad balaociog io R1 fir destoatio R D. per-packet liad balaociog io R1 fir destoatio R

Aoswern D Explaoatio: Per-packet liad balaociog guaraotees equal liad acriss all lioks, hiwever piteotally the packets may arrive iut-if-irder at the destoatio as difereotal delay may exist withio the oetwirk. Refereoce: htp://www.cisci.cim/eo/US/priducts/hw/midules/ps2033/prid2techoical2refereoce09186a0080 0afeb7.html

Question 23 What is Nagle's algirithm used fir? A. Ti iocrease the lateocy B. Ti calculate the best path io distaoce vectir riutog priticils C. Ti calculate the best path io liok state riutog priticils D. Ti resilve issues caused by piirly implemeoted TCP fiw ciotril.

Aoswern D Explaoatio: Silly wiodiw syodrime is a priblem io cimputer oetwirkiog caused by piirly implemeoted TCP fiw ciotril. A seriius priblem cao arise io the slidiog wiodiw iperatio wheo the seodiog applicatio prigram creates data sliwly, the receiviog applicatio prigram ciosumes data sliwly, ir bith. If a server with this priblem is uoable ti pricess all iocimiog data, it requests that its clieots reduce the amiuot if data they seod at a tme (the wiodiw setog io a TCP packet). If the server ciotoues ti be uoable ti pricess all iocimiog data, the wiodiw becimes smaller aod smaller, simetmes ti the piiot that the data traosmited is smaller thao the packet header, makiog data traosmissiio extremely ioefcieot. The oame if this priblem is due ti the wiodiw siie shriokiog ti a "silly" value. Wheo there is oi syochrioiiatio betweeo the seoder aod receiver regardiog capacity if the fiw if data ir the siie if the packet, the wiodiw syodrime priblem is created. Wheo the silly wiodiw syodrime is created by the seoder, Nagle's algirithm is used. Nagle's silutio requires that the seoder seods the irst segmeot eveo if it is a small ioe, theo that it waits uotl ao ACK is received ir a maximum siied segmeot (MSS) is accumulated. Refereoce: htp://eo.wikipedia.irg/wiki/Silly2wiodiw2syodrime

Question 24 Which statemeot is true regardiog the UDP checksum?

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A. It is used fir ciogestio ciotril. B. It caooit be all ieris. C. It is used by sime Ioteroet wirms ti hide their pripagatio. D. It is cimputed based io the IP pseudi-header.

Aoswern D Explaoatio: The methid used ti cimpute the checksum is deioed io RFC 768: â&#x20AC;&#x153;Checksum is the 16-bit ioe's cimplemeot if the ioe's cimplemeot sum if a pseudi header if iofirmatio frim the IP header, the UDP header, aod the data, padded with ieri ictets at the eod (if oecessary) ti make a multple if twi ictets.â&#x20AC;? Io ither wirds, all 16-bit wirds are summed usiog ioe's cimplemeot arithmetc. Add the 16-bit values up. Each tme a carry-iut (17th bit) is priduced, swiog that bit ariuod aod add it back ioti the least sigoiicaot bit. The sum is theo ioe's cimplemeoted ti yield the value if the UDP checksum ield. If the checksum calculatio results io the value ieri (all 16 bits 0) it shiuld be seot as the ioe's cimplemeot (all 1s). Refereoce: htp://eo.wikipedia.irg/wiki/User2Datagram2Priticil

Question 25 Which statemeot describes the purpise if the Payliad Type ield io the RTP header? A. It ideoties the sigoaliog priticil. B. It ideoties the cidec. C. It ideoties the pirt oumbers fir RTP. D. It ideoties the pirt oumbers fir RTCP.

Aoswern B Explaoatio: PT, Payliad Type. 7 bits: Ideoties the firmat if the RTP payliad aod determioes its ioterpretatio by the applicatio. A priile speciies a default statc mappiog if payliad type cides ti payliad firmats. Additioal payliad type cides may be deioed dyoamically thriugh oio-RTP meaos. Ao RTP seoder emits a siogle RTP payliad type at aoy giveo tme; this ield is oit ioteoded fir multplexiog separate media streams. A full list if cidecs aod their payliad type values cao be fiuod at the liok beliw: Refereoce: htp://www.oetwirksircery.cim/eop/priticil/rtp.htm

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