Subject: RFC 3056

From: [email-masked]
Date: Fri, 1 Feb 2002 13:00:10 +0100

Hello,

When reading RFC 3056 (6 to 4 strategy), I have 2 questions I could not 
get answered. Consider the router that originates the IPv4 tunnel. Which 
IP address should this router use as the source IP addres in its IPv4 
encapsulation header:

* Should this address be the router id of this router?
Or
* Should the source IPv4 address be derived from the source IPv6 address
Or
...?

Thanks for any help you can provide,

        Francis.

---

From: Pekka Savola <[email-masked]>
Date: Fri, 1 Feb 2002 16:34:17 +0200 (EET)

> * Should this address be the router id of this router?

If router-id is V4ADDR in 2002:V4ADDR.

> * Should the source IPv4 address be derived from the source IPv6 address

Yes.

See RFC3056 Chapter 3:

   IPv6 packets are transmitted in IPv4 packets [RFC 791] with an IPv4
   protocol type of 41, the same as has been assigned [MECH] for IPv6
   packets that are tunneled inside of IPv4 frames.  The IPv4 header
   contains the Destination and Source IPv4 addresses.  One or both of
   these will be identical to the V4ADDR field of an IPv6 prefix formed
   as specified above (see section 5 for more details).  The IPv4 packet
   body contains the IPv6 header and payload.

(btw, this is ngtrans, rather than ipng, material)

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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---

From: Brian E Carpenter <[email-masked]>
Date: Fri, 01 Feb 2002 17:50:44 +0100

I'm not sure about Pekka's answer, because I'm not sure what the question is.

The outer IPv4 packet is just a normal packet from the 6to4 router, so its
IPv4 source address is the IPv4 address of the sending interface on the
6to4 router. 

The inner IPv6 packet has an IPv6 source address which is that
of the originating IPv6 host. If the router is a normal 6to4 router, that
will be an IPv6 address starting with 2002:v4addr where v4addr is the source
IPv4 address of the 6to4 router. If the router is a 6to4 relay router,
the IPv6 source address could be any valid unicast IPv6 address (except for 
a few odd cases such as link local).

As Pekka says, this is an ngtrans topic.

   Brian