276 Understanding IPv6,Second Edition There is a common misconception that before you can begin experimenting with IPv6 connectivity and application migration,you must deploy native IPv6 addressing and rout- ing,which requires a detailed analysis of IPv6 addressing schemes,router updates and configuration,and a rollout schedule.Although this should eventually be done for intra- nets,ISATAP allows you to turn the IPv4-only portion of your intranet into a logical IPv6 subnet.Once this subnet is defined and assigned a global or unique local prefix,IPv6/IPv4 hosts that support ISATAP can use ISATAP-based addresses for IPv6 connectivity.ISATAP allows you to make your IPv4-only intranet IPv6-capable,without requiring modifications to your existing router infrastructure to support native IPv6 addressing and routing. With ISATAP,you can immediately begin experimenting with IPv6 connectivity and application migration. ISATAP allows you to phase in the native IPv6 addressing and routing capability on your intranet in the following way: Phase 1:IPv4-only intranet In this phase,your entire intranet can be a single,logical ISATAP subnet. Phase 2:IPv4-only and IPv6-capable portions of your intranet In this phase, your intranet has an IPv4-only portion(the logical ISATAP subnet)and an IPv6-capable portion.The IPv6-capable portion of your intranet has been updated to support native IPv6 addressing and routing. Phase 3:IPv6-capable intranet In this phase,your entire intranet supports both IPv4 and native IPv6 addressing and routing and ISATAP is no longer needed. With ISATAP,you can have IPv6 connectivity between hosts and applications during the first two phases of the transition from an IPv4-only to an IPv6-capable intranet. ISATAP Tunneling ISATAP-based IPv6 traffic is tunneled or encapsulated with an IPv4 header,also known as IPv6-over-IPv4 traffic.For the details of IPv6-over-IPv4 traffic,see Chapter 11,"IPv6 Transition Technologies."This tunneling is automatically done by an ISATAP tunneling interface on the sending host or forwarding router.The ISATAP tunneling interface treats the entire IPv4-only portion of the intranet as a single link layer,in much the same way as Ethernet.In the case of ISATAP,the link-layer encapsulation is IPv4. The IPv6 protocol for Windows Server 2008 and Windows Vista creates a separate ISATAP tunneling interface for each LAN interface that is installed in the computer that has a different DNS suffix.For example,if a computer running Windows Vista has two LAN interfaces and they are both attached to the same intranet and are assigned the same DNS suffix,there is only one ISATAP tunneling interface.If these two LAN interfaces are attached to two different networks with different DNS suffixes,there are two ISATAP tunneling interfaces.For￾    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  ,"$#2' ("$"$"$"%")121 )1 ,766-(%"$5 > ? FABCDECGHDG  IEJ  ,"$#2 ' ("$"$",-.83 "1'# $ "K$1 )1,766-(%"$L"0",-./3#%1 # $ "5,-./3#%1# $ " &' ("$"$%"(#0$0$ (## $"$. ,-./00")"0 ($")5 > ? MACGHD  ,"$#2' ("$"$"$(## $% $,-.8 "0"$.,-./00")"0 ($")"0,766-" 1 ")"005 <$,766-2' (".,-./ ""$.$'%$+" $"0##1$ "0(")$&$ $+ # &$$"$ "& !",-.83 "1'$ ",-./3#%1"$"$5 NONOJD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