通过ipsec配置隧道通用路由封装模块3 iscw10s04l04.pptx

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通过ipsec配置隧道通用路由封装模块3 iscw10s04l04.pptx

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IPsecVPNsConfiguringGRETunnelsoverIPsec

GenericRoutingEncapsulation

GenericRoutingEncapsulationOSILayer3tunnelingprotocol:UsesIPfortransportUsesanadditionalheadertosupportanyotherOSILayer3protocolaspayload(e.g.,IP,IPX,AppleTalk)

DefaultGRECharacteristicsTunnelingofarbitraryOSILayer3payloadistheprimarygoalofGREStateless(noflowcontrolmechanisms)Nosecurity(noconfidentiality,dataauthentication,orintegrityassurance)24-byteoverheadbydefault(20-byteIPheaderand4-byteGREheader)

OptionalGREExtensionsGREcanoptionallycontainanyoneormoreofthesefields:TunnelchecksumTunnelkeyTunnelpacketsequencenumberGREkeepalivescanbeusedtotracktunnelpathstatus.

GREConfigurationExampleGREtunnelisupandprotocolupif:TunnelsourceanddestinationareconfiguredTunneldestinationisinroutingtableGREkeepalivesarereceived(ifused)GREisthedefaulttunnelmode.

IntroducingSecureGRETunnels

IntroducingSecureGRETunnelsGREisgoodattunneling:MultiprotocolsupportProvidesvirtualpoint-to-pointconnectivity,allowingroutingprotocolstobeusedGREispooratsecurity—onlyverybasicplaintextauthenticationcanbeimplementedusingthetunnelkey(notverysecure)GREcannotmodatetypicalsecurityrequirements:ConfidentialityDatasourceauthenticationDataintegrity

IPsecCharacteristicsIPsecprovideswhatGRElacks:Confidentialitythroughencryptionusingsymmetricalgorithms(e.g.,3DESorAES)DatasourceauthenticationusingHMACs(e.g.,MD5orSHA-1)DataintegrityverificationusingHMACsIPsecisnotperfectattunneling:OlderCiscoIOSsoftwareversionsdonotsupportIPmulticastoverIPsecIPsecwasdesignedtotunnelIPonly(nomultiprotocolsupport)UsingcryptomapstoimplementIPsecdoesnotallowtheusageofroutingprotocolsacrossthetunnelIPsecdoesnottunnelIPprotocols;GREdoes

GREoverIPsecGREoverIPsecistypicallyusedtodothefollowing:Createalogicalhub-and