Partial Use Of one Regions IP Block in another

Owen DeLong owen at
Thu May 20 16:36:02 UTC 2010

On May 20, 2010, at 9:14 AM, George Bonser wrote:

>> -----Original Message-----
>> From: Owen DeLong [mailto:owen at]
>> Sent: Thursday, May 20, 2010 7:37 AM
>> To: Net
>> Cc: nanog at
>> Subject: Re: Partial Use Of one Regions IP Block in another
>> You state "Obv, the best approach...". I don't think so. I think the
>> best
>> approach is whatever allows you to make most efficient use of your
>> address space. Usually this will be from a single RIR rather than a
>> multiple RIR approach.
>> Owen
> The one drawback to that would be people who attempt to do geographical
> based service provisioning. Say a company based in the US uses part of
> their block in Europe or APAC.  When they do a DNS request for a service
> address from $GLOBAL_CONTENT_PROVIDER, they end up getting the US
> service address because the content provider believes the request is
> coming from the US resulting in poor performance.  In other words, if a
> service relies on connection to other services that try to do
> geographical affinity, it could lead to a sub-optimal experience.
I have ZERO sympathy for people who attempt to do this getting wrong
answers.  There is little correlation between geography and IP addresses.

In fact, I know lots of people who consider it a benefit to have ARIN addresses
in other parts of the world because it allows them to get to content that isn't
allowed to APNIC addresses on the belief that this somehow protects
copyright or other issues for content distribution. I find that pretty amusing.

> It could also cause problems where the content is different (or possibly
> prohibited) depending on the geographical location of the requestor
> which some folks try to determine by source address (but which is
> actually quite idiotic, in my opinion, because as you see from this
> thread, an IP address in no way relates to where the person really is,
> it only relates to where the entity to whom it was issued is located).
Again, ZERO sympathy here.  Especially where someone is trying to
use source IP as a mechansim for determining who they are willing
to distribute their content to. 

> Been there and experienced issues like that before.  It can even be bad
> when you are given an IP block that might have been used before by
> someone in another region.
Can be bad when given an IP block that might have been used before
by someone in the same region.  That's not particularly different.

Can be bad if you get space from one of the more recent /8s that has
lots of cruft from having been used as pseudo-RFC-1918 space, too.

We're scraping the bottom of the barrel for IPv4 space these days.
It is what it is, and it's only going to get worse in IPv4.  Time to go
to IPv6.


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