NATLL6 [was Re: Forwarding Packets With Link Local Destination Addresses]

Brian E Carpenter <brian.e.carpenter@gmail.com> Fri, 08 January 2021 19:37 UTC

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Subject: NATLL6 [was Re: Forwarding Packets With Link Local Destination Addresses]
To: Alejandro Acosta <alejandroacostaalamo@gmail.com>, ipv6@ietf.org
References: <DM6PR05MB6348A18046C5DDC7CF2AED76AEAF0@DM6PR05MB6348.namprd05.prod.outlook.com> <561e3133-73c9-6ded-0311-838d5939dcd2@gmail.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Message-ID: <605db208-e458-58ec-5872-932e0b9f9b38@gmail.com>
Date: Sat, 9 Jan 2021 08:37:13 +1300
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On 08-Jan-21 14:34, Alejandro Acosta wrote:
> Hello,
> 
>   My apologies for using this thread, I have a valid point. My comment inline:

Subject header tweaked accordingly...

> On 7/1/21 1:53 PM, Ron Bonica wrote:
>>
>> Folks,
>>
>>  
>>
>> According to RFC 4291, “routers must not forward any packets with Link-Local source or destination addresses to other links”.
>>
>>  
>>
>> I interpret this statement to include packets that contain routing headers. For example, it forbids an SRv6 packet whose final segment has a locator that begins with FE80.
>>
>   In LACNIC we ran a project called Natmeter [1] for about 2 years, we obtained a lot of interesting data during this period [2].
> 
>   The case is the following, we detected some end-user devices with only Link Local addresses (exactly, no GUA nor ULA) that were successfully natted and using the web.
> 
>   Is it ok?, do you consider it as a forwarding of a packet? was it a crazy result? (we saw few samples of this)

NAT66 is not defined and not recommended, so there really isn't an answer to your questions. I can't think of a reason why such a hack wouldn't work, though. As long as the LL address is translated, it will not escape from the LAN.

Regards
     Brian

> 
> 
> Thanks,
> 
> 
> [1] https://prensa.lacnic.net/news/en/research/lacnic-project-detects-massive-presence-of-nat-boxes-in-the-region
> 
> [2] Well, actually it still available with much less successful measurement
> 
> 
>>  
>>
>> Does everyone share this interpretation? If so, do RFC 4291 or RFC 8200 make this sufficiently clear?
>>
>>  
>>
>>                                                                                                    Ron
>>
>>
>> Juniper Business Use Only
>>
>>
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