[6bone] Cisco, NAT-PT : establish connection from IPv6 to IPv4

[Jerome Wenzel]

Hello,

I'm testing NAT-PT on a 7200 Cisco router, and I would like to establish
connection between the IPv6 and the IPv4 networks.

I've mapped the IPv6 address of my PC, which is on an IPv6 only network,
to an IPv4 address. So, my IPv6 PC is accessible by any IPv4 PC.
If I ping it, I can see the encapsulation of the packet coming from the
IPv4 PC, it's like PREFIX::IPv4_address_in_hexadecimal_form. The
translation table of the router is updated. Then, the IPv6 PC can ping
the IPv4 PC, because of this update.

But now I want to ping another IPv4 PC, so I type : ping6
PREFIX::another_IPv4_address. The router receives IPv6 packets, but drop
them (I saw this with debug ipv6 packet). On the url join below, it
seems to be normal, because translation doesn't exists for the incoming
packet.

How can I process to access any IPv4 adress ? I must create a mapping ?
It doesn't seem to be practical.
Why from IPv6 to IPv4 isn't the IPv6 header (like PREFIX::IPv4_address)
automatically translated to an IPv4 header, as it is done from IPv4 to
IPv6 ?

Thanks.

This the url where I've found some informations :

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_data_she
et09186a008011ff51.html

...

5 NAT-PT translations and Application Level Gateway
5.1 IP header translation
5.1.1 From IPv6 to IPv4
The Protocol Translator translates the IPv6 header to an IPv4 header
under the following conditions:

IPv6 packet is received with an IPv4-mapped IPv6 address (i.e.
pre-configured /96 prefix) 
Translation exists for the incoming packet 

...

5.1.2 From IPv4 to IPv6
When NAT-PT receives a packet addressed to a destination that lies
outside of the attached IPv4 realm, the IPv4 header is translated to an
IPv6 header.

...