Subject: RFC 3056

From: [email-masked]
Date: Thu, 28 Feb 2002 08:56:28 +0100

Hi,

I have a question on the relay router in the 6to4 transition model of RFC 
3056:

        R1 (6to4 router) -- R2 (IPv4) -- R3 (IPv4) -- R4 (relay router)

Note: R1 is a pure 6to4 router; R2 and R3 are part of the IPv4 cloud; R5 
is a relay router.

In the 6to4 model R1 and R4 need to have a 6to4 address. From RFC 3056 I 
understand that these 6to4 addresses have to be configured on the 
interface between R1 and R2 (R4 and R3) respectively. I am now puzzled 
between the following 2 observations:
1) I would also expect to have an IPv6 address configured on R2's end of 
the R1-R2 interface. After all, only configuring an IPv6 address on 1 of 
the routers connected to an interface would be a bit strange? A similar 
remark holds for R3 on the R4-R3 interface.
2) However, no IPv6 address should be assigned to R2 (R3) since R2 (R3) is 
only IPv4 capable?

Can somebody clarify the apparent contradiction between both statements? 
Thanks.

        Francis.

---

From: Pekka Savola <[email-masked]>
Date: Thu, 28 Feb 2002 12:21:55 +0200 (EET)

> 2) However, no IPv6 address should be assigned to R2 (R3) since R2 (R3) is 

It's 6to4 _pseudo_ - interface :-).  It's not assigned (normally) on any
physical link.  The only address you need between R1-R2 and R3-R4 are IPv4
addresses (from which, a 6to4 address may be derived from).

HTH,

-- 
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: "Tony Hain" <[email-masked]>
Date: Thu, 28 Feb 2002 09:34:38 -0800

> addresses (from which, a 6to4 address may be derived from).

In case that was not clear; the IPv6 address on R1 & R4 are assigned to
the pseudo interface that forms a logical point-to-point tunnel over the
physical interfaces with IPv4 addresses.

Another way to look at it is to consider the IPv4 components to be the
logical equivalent of a multi-point Layer-2 network (like frame relay or
ATM) so the IPv4 wrapper becomes just another framing wrapper for the
2002::/16 IPv6 subnet.

Tony