On 08/11/2013 07:56, Fred Baker (fred) wrote:
> On Nov 7, 2013, at 10:42 AM, 神明達哉 <[email protected]>
>  wrote:
> 
>> At Thu, 7 Nov 2013 17:58:56 +0100,
>> Jen Linkova <[email protected]> wrote:
>>
>>> Looks like we (finally) have a chance to enforce the requirement from
>>> RFC4007, Section9:
>>>
>>> "If transmitting the packet on the chosen next-hop interface
>>> would cause the packet to leave the zone of the source
>>> address, i.e.,
>>> cross a zone boundary of the scope of the
>>> source address, then the packet is discarded. "
>>>
>>> I'm seeing plenty of packets from link-local sources to global
>>> destinations which means that:
>>> 1) there are hosts with broken default address selection
>>> AND
>> (Probably an off-topic in this context but) this is not necessarily
>> accurate.  If a host only has a link-local address but somehow knows
>> the interface to send packets to a global destination, it would be
>> able to send packets with source being link-local and destination
>> being global, and validly (not breaking RFC 6724) so.  I believe it's
>> more likely to be a broken network configuration than a broken host
>> implementation.
> 
> I suspect it's some of each. The host should, I should think, set the hop 
> limit to one on any packet that is to a link-local address, to ensure that 
> the packet is not repeated by a broken router (apart from protocols that ask 
> to have it set to 255 and have the receiving host check for that value). 
> Also, upstream network's BCP 38 implementation sounds suspect, and I'm with 
> Jen in wondering why a router forwarded the packet in the first place.

Are you sure these packets come from hosts? There is a known case
which is a router generating ICMP reply packets that has no GUA
configured since all its peers are link-local.

   Brian

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