Figure 3-5 Working Principle Of Ipv4 (Or Ipv6) Over Ipv6 Tunnel - Zte ZXR10 ZSR V2 Series Product Description

ZXR10 ZSR V2 Series Router Product Description

Figure 3-5 Working principle of IPv4 (or IPv6) over IPv6 tunnel

3.9.4.3 ISATAP
ISATAP (the Intra-Site Automatic Tunnel Addressing Protocol) can make the dual-stack
node at IPv4 site get access to IPv6 router by automatic tunnel. It's permitted not to
share the dual-stack node of one physical link and transmit the data packet to next hop of
IPv6 through IPv4 automatic tunnel.
ISATAP transition system uses an IPv6 address with an IPv4 address embedded. No
matter what kind of IPv4 address is used at the site, global or private, IPv6-in-IPv4
automatic tunnel can be used at the site. ISATAP address format can use site unicast
IPv6 address prefix or global unicast IPv6 address prefix. That is to say, it can support
both site and global IPv6 route.
ISATAP tunnel principles cover tunnel encapsulation and de-encapsulation process:

Encapsulation principles: When IPv6 packets are transmitted, the egress is the
tunnel interface. The tunnel type can be decided based on the packets returned by
the interface. If it is ISATAP tunnel, we take IPv4 header encapsulation. ISATAP
tunnel encapsulation format inherits that for 6in4. The destination address of outer
layer V4 is the V4 address embedded in destination address of V6 packet. The
source address of outer layer V4 is the source address configured for ISATAP
tunnel. After the encapsulation common IPv4 packets are transmitted to take the
processing.
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