Convention for embedding IPv4 into IPv6?

[John Biederstedt]

All,

I read in rfc 4038 that representing IPv4 address in an IPv6 address should be like 2001::FFFF:192.168.1.1, which would be  2001::FFFF:c0a8:101, or 2001.2.3.4::FFFF:192.168.1.1 (2001:2:3:4:0:ffff:c0a8:101).  However, setting up NAT-PT any 96 bit prefix will work.  So I'm wondering if the standard set forth in rfc4038 (its informational) really applies to NAT-PT, or just for IPv4 applications not being natted (which doesn't make sense unless some other 4to6 mechanism is involved). 

Any thoughts?

John

[fabios]

John,

it is not very clear what are you trying to achieve by "embedding" ipv4 (address|traffic) into ipv6.

By what you are discussing apperaars you are talking about the rappresentation of an IPv4 address into an IPv6 address field. Fact is that all bit being born equal they mean differently based on contest.

Each 4 hex digit are 16 bit and two groups of 4 hex digits (any)  can contain and IPv4 address.

So an IPv4 compatible IPv6 address would be 0:0:0:0:0:0:192.168.1.1 which can also be rapresented as ::c0a8:101.

What that means and how edge routers/devices and gateway would handle such address depends on context/configuration. 6to4 6rd autotunnels ipv4 compatible ipv6 and ISATAP tunnels carry within their address field tunnel end point/ipv4 destination addresses that are extracted and used to route traffic.

I know I did not clear the issue up but it really depends on what you are doing/trying to achieve how you embed an ipv4 address (of what) in an IPv6 address field and what that meas.

I would definitely recommand:

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-addrg_bsc_con_ps10890_TSD_Products_Configuration_Guide_Chapter.html#wp1038821

and

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-tunnel_ps10890_TSD_Products_Configuration_Guide_Chapter.html#wp1055999

Actually the whole book is a good read.

Hope this helps

Cheers

Fabio