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Re: [v6ops] Q about IPv4-mapped IPv6 address & MPLS

"Rajiv Asati (rajiva)" <rajiva@cisco.com> Thu, 01 May 2014 22:21 UTC

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From: "Rajiv Asati (rajiva)" <rajiva@cisco.com>
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
Thread-Topic: [v6ops] Q about IPv4-mapped IPv6 address & MPLS
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Date: Thu, 01 May 2014 22:21:22 +0000
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References: <CF875D2F.1951A9%rajiva@cisco.com> <20140501085939.GG43641@Space.Net>, <5362B2BD.7060602@gmail.com>
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Cc: "mpls@ietf.org" <mpls@ietf.org>, "v6ops@ietf.org" <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>
Subject: Re: [v6ops] Q about IPv4-mapped IPv6 address & MPLS
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Thanks, Brian. Which RFC 4038 section in particular should be referenced to?

Cheers,
Rajiv

> On May 1, 2014, at 4:47 PM, "Brian E Carpenter" <brian.e.carpenter@gmail.com> wrote:
> 
>> On 01/05/2014 20:59, Gert Doering wrote:
>> Hi,
>> 
>>> On Thu, May 01, 2014 at 06:08:51AM +0000, Rajiv Asati (rajiva) wrote:
>>> We need your guidance on handling v4-mapped v6 addresses (section 2.5.5.2
>>> of [RFC4291]). 
>>> 
>>> 1. Should/Would they appear in IPv6 routing table?
>> 
>> "Yes and no".  It depends on the context - if the packet comes in and has
>> an IPv6 header, address lookup happens via the IPv6 routing table.  If 
>> a packet comes in with an IPv4 header, address lookup happens via the
>> IPv4 routing table.  
>> 
>> So, IPv4 should never "bleed over" to the IPv6 routing table, but if 
>> you happen to receive an IPv6 packet with a destination IPv6 address
>> in it's header of ::ffff:1.2.3.4, you'd either drop it right away,
>> or use the IPv6 routing table to find the destination.
>> 
>> The router itself should never ever source packets with a v4-mapped
>> destination address in the packet (see below).
>> 
>>> 2. Should an IPv6 packet with ::FFFF:127.0.0.0  be forwarded or dropped or
>>> treated as a loopback packet, if ever received?
>> 
>> Dropped.  v4-mapped is an internal representation of an IPv4 address
>> recevied on an ipv6 socket, and should never ever appear in packets on
>> the wire.
> 
> Nobody seems to have mentioned RFC 4038, which makes this very clear.
> These addresses are an artefact and have no place in the routing
> system as such, and still less on the wire.
> 
>    Brian
>

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