How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption")

Rob McEwen rob at
Fri Oct 2 03:58:12 UTC 2015

On 10/1/2015 11:44 PM, Mark Andrews wrote:
> IPv6 really isn't much different to IPv4.  You use sites /48's
> rather than addresses /32's (which are effectively sites).  ISP's
> still need to justify their address space allocations to RIR's so
> their isn't infinite numbers of sites that a spammer can get.

A /48 can be subdivided into 65K subnets. That is 65 *THOUSAND*... not 
the 256 IPs that one gets with an IPv4 /24 block. So if a somewhat legit 
hoster assigns various /64s to DIFFERENT customers of theirs... that is 
a lot of collateral damage that would be caused by listing at the /48 
level, should just one customer be a bad-apple spammer, or just one 
legit customer have a compromised system one day.

Conversely, if a more blackhat ESP did this, but it was unclear that 
this was a blackhat sender until much later.. then LOTS of spam would 
get a "free pass" as individual /64s were blacklisted AFTER-THE-FACT, 
with the spammy ESP still having LOTS of /64s to spare.. remember, they 
started with 65 THOUSAND /64 blocks for that one /48 allocation (Sure, 
it would eventually become clear that the whole /48 should be blacklisted).

other gray-hat situations between these two extremes can be even more 
frustrating because you then have the same "free passes" that the 
blackhat ESP gets... but you can't list the whole /48 without too much 
collateral damage.

SUMMARY: So even if you moved into blocking at the /64 level, the 
spammers have STILL gained an order of magnitudes advantage over the 
IPv4 world.... any way you slice it. And blocking at the /48 level WOULD 
cause too much collateral damage if don't indiscriminately.

And this is assuming that individual IPs are NEVER assigned individually 
(or in smaller-than-/64-allocations) . (maybe that is a safe assumption? 
I don't know? regardless, even if that were a safe assumption, the 
spammers STILL have gained a massive advantage)

Rob McEwen
+1 478-475-9032

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