[RFCI-Discuss] IPv6 and BogusMX

[Jimmy Hess]

Derek J. Balling wrote:
>> Some domains may use intentionally unavailable MXes as part of an
>> anti-spam scheme, but
>> the IPs  used should have proper RDNS, and at least one mail server
>> operational at all times.
>
> Unavailable is one thing, but using "1918" space is not "unavailable" 
> as "your" 1918 space and "mine" might collide. :-)
>
> cheers,
> D
If you're using ULA addresses, no.     Unique Local Addresses  are not 
supposed to collide, your space and mine should
never collide like 1918 space could, because if we both follow the RFC 
with our ULA addresses, the algorithm used to
generate these addresses is robust enough to assure of their 
uniqueness,  see  rfc4193.

Though it doesn't really stop it from being a bogus address.
For a "host"  listed in a MX  to be legitimate, it should be part of a 
globally allocated netblock
complete with whois records indicating contacts for "operator"s of the 
live (or dead) hosts on that network.


Link-local addresses are definitely bogus too.

That possibility exists with link-local (but non-ULA address) that your 
assigned address could clash with
mine;  granted the probability of you happening to generate the 
addresssomeone else randomly generated
(or generated based on their MAC address)  is small,  there is less 
assurance of their uniqueness.

Link-local addresses aren't like 1918 address either though, since they 
only exist on a local physical network

(These addresses aren't supposed to be routable even within your private 
site, much like ARP protocol traffic
isn't meant to be routable, hence link-local.)


--
-Mysid