Zte ZXR10 ZSR V2 - Chapter 16 Ipv6 Tunnel Configuration; Figure 16-4 Principles of a 6 To4 Tunnel

Chapter16IPv6TunnelConguration
lEncapsulation:IfthepacketegressinterfaceisatunnelinterfacewhenanIPv6host
orroutersendsanIPv6ow,thehostorrouterrstdeterminesthetunneltype.If
thetunnelisa6in4tunnel,thehostorrouterimplementsIPv4headerencapsulation.
Duringtheencapsulation,thesourceanddestinationaddressesoftheIPv4header
aremanuallyconguredbytheuser.Theencapsulatedpacketisthensentaccording
totheIPv4packetsendingprocess.
lDecapsulation:Theprocessisjustcontrarytotheencapsulationprocess.Ifthe
protocolnumberintheIPv4headerofthereceivedIPv4packetis41,thehostorrouter
proceedstothe6in4decapsulationprocessandsearchesforthematchedtunnel
numberaccordingtothesourceanddestinationaddressesofthepacket.Ifthetunnel
numberisfound,thehostorrouterremovestheIPv4headeraddedduringtunnel
encapsulationanddeliverstheremainingIPv6packettotheIPv6packetreceiving
processforfurtherhandling.
6to4Tunnel
Figure16-4showstheoperatingprinciplesofa6to4tunnel.
Figure16-4Principlesofa6to4Tunnel
A6to4tunnelisapoint-to-multipointautotunnelusedtoconnectmultipleisolatedIPv6sites
throughanIPv4networktoanIPv6network.Itmakespossibletheautomaticacquisition
oftheIPv4addressattheterminationpointofthetunnelbyembeddinganIPv4address
inthedestinationaddressofanIPv6packet.
The6to4tunnelassumesaspecial6to4addressintheformatof2002:abcd:efgh:Subnet
ID::InterfaceID/64.Oftheaddress,2002isaxedIPv6addressprex,abcd:efghisa
globallyunique32-bitIPv4sourceaddressofthe6to4tunnelinhexadecimal(e.g.1.1.1.1
canbeexpressedas0101:0101),andtherestuniquelyidentiesthepositionofahostin
a6to4network.Astheterminationpointofthetunnelcanbeautomaticallydeterminedby
thisembeddedIPv4address,tunnelestablishmentisveryconvenient.
Becausethe16-bitsubnetIDinthe64-bitaddressprexofthe6to4addresscanbe
user-denedwhereastherst48bitsoftheprexareaxednumberordeterminedby
theIPv4addressofthedeviceatthestartorterminationpointofatunnel,itispossibleto
forwardIPv6packetsoverthetunnel.The6to4tunnelmakespossibletheinterconnection
16-3
SJ-20140504150128-018|2014-05-10(R1.0)ZTEProprietaryandCondential