second gateway and an IPv4 address designated by the
second gateway, the second gateway is one of a device connecting an IPv6
network to an IPv4 network and a device connecting a layer 2 network to
an IPv4 network, and IPv6 addresses of all IPv6 terminals connected to
the second gateway comprise the same IPv4 address.

5. The method according to claim 4, wherein if the IPv4 address is a
compressed IPv4 address, the encapsulating, by the first gateway, the
IPv6 packet in an IPv4 packet of which a destination address is the IPv4
address comprises: recovering, by the first gateway, the compressed IPv4
address, and encapsulating the IPv6 packet in an IPv4 packet of which a
destination address is the recovered IPv4 address.

6. The method according to claim 5, further comprising: according to a
specific field value thatto the gateway include the same IPv4 address. The
IPv6 terminal sends an IPv6 packet to the gateway, where IPv6 packet
includes the IPv6 address as a source address.

[0006] In a second aspect, an embodiment of the present disclosure
provides a method for transmitting an IPv6 packet in an IPv4 network. In
the method, a first gateway receives an IPv6 packet sent by an IPv6
terminal, where the IPv6 packet includes a destination IPv6 address. If
the destination IPv6 address includes an IPv4 address, the first gateway
encapsulates the IPv6 packet in an IPv4 packet of which a destination
address is the IPv4 address, and sends the IPv4 packet to a second
gateway. The IPv4 address included in the destination IPv6 address
includes an IPv4 address of the second gateway or an IPv4 address
designated by the second gateway.