Advantages
Anotheradvantageofusingstaticroutingisthehighnetworksecurityandconfidentiality.Dynamicroutingrequiresrouterstofrequentlyexchangetheirrespectiveroutingtables,andtheanalysisoftheroutingtablecanrevealinformationsuchasthenetworktopologyandnetworkaddresses.Therefore,thenetworkcanalsousestaticroutingforsecurityconsiderations.Doesnotoccupynetworkbandwidth,becausestaticroutingdoesnotgenerateupdatetraffic.Staticroutingissuitableforsmallandmedium-sizednetworks.
Disadvantages
Staticroutingisusuallynotsuitableforlargeandcomplexnetworkenvironments.Ontheonehand,itisdifficultfornetworkadministratorstofullyunderstandthetopologyoftheentirenetwork;ontheotherhand,whenthetopologyandlinkstatusofthenetworkchange,thestaticroutinginformationintherouterneedstobeadjustedonalargescale,whichisdifficult.Andthecomplexityisveryhigh.Whenthenetworkchangesorthenetworkfails,theroutecannotbereselected,whichmaycausetheroutetofail.
Configurationcommands
(TakeFigure1asanexample)
Therearetwowaystoconfigurestaticrouting:staticroutingwithanext-hoprouter,andSendoutthestaticrouteoftheinterface
router(config)#hostnameA(changerouterhostname)A(config)#interfacef0/0(enterinterfacef0/0)
A(config-if)#ipaddress192.168.1.1255.255.255.0(Settheinterfaceipaddressandsubnetmask)
A(config-if)#noshutdown(Enabletheinterface)
A(config)#interfacef0/1
A(config-if)#ipaddress192.168.2.1255.255.255.0
A(config-if)#noshutdown
×××Chooseoneofthefollowingtwo:
A(config)#iproute192.168.3.0255.255.255.0f0/1(targetnetworksegmentIPaddresstargetsubnetmasksendinginterface(routerA))
or
A(config)#iproute192.168.3.0255.255.255.0192.168.2.2(targetnetworksegmentIPaddresstargetsubnetmasknextrouterinterfaceipAddress)
×××
router(config)#hostnameB
B(config)#interfacef0/0
B(config-if)#ipaddress192.168.3.1255.255.255.0
B(config-if)#noshutdown
B(config)#interfacef0/1
B(config-if)#ipaddress192.168.2.2255.255.255.0
B(config-if)#noshutdown
×××Chooseoneofthefollowing:
B(config)#iproute192.168.1.0255.255.255.0192.168.2.1
Or:
B(config)#iproute192.168.1.0255.255.255.0f0/1(targetnetworksegmentIPaddresstargetsubnetmaskoutputinterface(routerB))
×××
Note1:ThisnetworklinkisanEthernetlinkIfitisaseriallink,thesendinginterfaceisalsotheserialinterfaceofthelocalrouter.
Conciseexplanation:iproute192.168.3.0255.255.255.0192.168.2.2
Thissentencemeans:OnHOSTA,therouterseesthatthedestinationnetworksegmentis192.168.3.0Datapacket,sendthedatapacketto192.168.2.2
Note2:iproutecanpointtoone,ifbothareconfigured,itmeansthatthedatapacketissentoutfromfa0/1,Andtheothersaidthatdatapacketsweresenttothisip(forexample,192.168.2.2).Tworepetitions.GenerallywesetittopointtotheIP.
Whentherearetwoormorestaticroutespointingtothesamedestinationaddressbutdifferentegressesonthesameroutingorswitchingdevice,thetrafficsenttothedestinationaddresswillbeloadbalancedfromtheseegresses.
Example
ThebasicstaticroutingexampleisshowninFigure2.ItconsistsoftworoutersR1andR2(theinterfacenumberandIPaddressaregiveninFigure2),whicharerespectivelyConnectedtotheirrespectivenetworks:R1isconnectedtothesubnet192.168.0.0/24,andR2isconnectedtothesubnet192.168.2.0/24.
Withoutconfiguringstaticrouting,computersAandBinthesetwosubnetscannotcommunicate.TheIPpacketsentfromcomputerAtocomputerB,afterreachingR1,R1doesnotknowhowtoreachthenetworksegment192.168.2.0/24wherecomputerBislocated(thatis,thereisnoroutingtableto192.168.2.0/24onR1),thesameR2alsodoesnotknowhowtoreachthenetworksegment192.168.0.0/24wherecomputerAislocated,sothecommunicationfails.
Atthistime,theadministratorisrequiredtoconfigurestaticroutesonR1andR2toenablecomputersAandBtocommunicatesuccessfully.
Executethecommandtoaddstaticrouteiproute192.168.2.0255.255.255.0192.168.1.1onR1.ItmeanstotellR1thatifthereisanIPpacketthatwantstoreachthenetworksegment192.168.2.0/24,thenpleasesendthisIPpacketto192.168.1.1(thatis,theoppositeendconnectedtoport2ofR1).
Atthesametime,executethecommandtoaddstaticroutesonR2iproute192.168.0.0255.255.255.0192.168.1.2.ItmeanstotellR2thatifthereisanIPpacketthatwantstoreachthenetworksegment192.168.0.0/24,thenpleasesendthisIPpacketto192.168.1.2(thatis,theoppositeendconnectedtoport3ofR2).
Throughtheabovetwoconfigurations,theIPpacketsentfromcomputerAtocomputerBcanbeforwardedtoR2byR1throughport2,andthenR2tocomputerB.Similarly,theIPpacketreturnedfromcomputerBtocomputerAcanbeforwardedtoR1byR2throughport3,andthenR1isforwardedtocomputerA,completingacompletecommunicationprocess.
FrequentlyAskedQuestions
1)Whyisthereadefaultroute
Theroutehastolookattheroutingtabletodeterminehowtoforwardthedatapacket,useTheconfigurationofstaticroutesonebyoneistediousanderror-prone.Iftherouterhasaneighborwhoknowshowtogettoalldestinations,itcandelegatethetaskofroutingtablematchingtoit,whichsavesalotofwork.
Forexample,thegatewaywillknowalltheroutes.Ifarouterisconnectedtothegateway,youcanconfigurethedefaultroutetoforwardalldatapacketstothegateway.
2)Whythedefaultrouteis0.0.0.0
WhenmatchinganIPaddress,0meanswildcard,anyvalueisfine.Therefore,thematchbetween0.0.0.0andanydestinationaddresswillsucceed,resultingintheeffectofthedefaultrouterequirement.