Ipv4 Over Ipv4 Tunneling - HP 6125XLG Layer 3-Ip Services Configuration Manual

6to4 tunneling—A point-to-multipoint automatic tunnel. It is used to connect multiple isolated IPv6
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networks over an IPv4 network. The destination IPv4 address of a 6to4 tunnel is embedded in the
destination 6to4 address of packets. This mechanism enables the device to automatically get the
tunnel destination address, simplifying tunnel establishment.
The 6to4 address format is 2002:abcd:efgh:subnet number::interface ID/48, where 2002 is the
fixed IPv6 address prefix, and abcd:efgh represents a 32-bit globally unique IPv4 address in
hexadecimal notation. For example, 1.1.1.1 can be represented by 0101:0101. The IPv4
address identifies a 6to4 network (an IPv6 network where all hosts use 6to4 addresses). The
border router of a 6to4 network must have the IPv4 address abcd:efgh configured on the interface
connected to the IPv4 network. The subnet number identifies a subnet in the 6to4 network. The
subnet number::interface ID uniquely identifies a host in the 6to4 network.
ISATAP tunneling—An ISATAP tunnel is a point-to-multipoint automatic tunnel. It provides a solution
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to connect an IPv6 host to an IPv6 network over an IPv4 network.
The destination addresses of IPv6 packets are all ISATAP addresses. The ISATAP address format is
prefix:0:5EFE:abcd:efgh. The 64-bit prefix is a valid IPv6 unicast address prefix. The
abcd:efgh/64 segments represent a 32-bit IPv4 address, which identifies the tunnel destination
but does not require global uniqueness.
ISATAP tunnels are mainly used for communication between IPv6 routers or between an IPv6 host
and an IPv6 router over an IPv4 network.
Figure 83 Principle of ISATAP tunneling

IPv4 over IPv4 tunneling

IPv4 over IPv4 tunneling (RFC 1853) enables isolated IPv4 networks to communicate. For example, an
IPv4 over IPv4 tunnel can connect isolated private IPv4 networks over a public IPv4 network.
Figure 84 IPv4 over IPv4 tunnel
Packets traveling through a tunnel undergo encapsulation and de-encapsulation, as shown in
Encapsulation:
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a. Device A receives an IP packet from an IPv4 host and submits it to the IP protocol stack.
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Figure 84.