How big a network is routed these days?

Joe Abley jabley at
Wed Jan 17 22:29:46 UTC 2007

On 17-Jan-2007, at 12:43, Marshall Eubanks wrote:

> On Jan 17, 2007, at 12:19 PM, David Freedman wrote:
>> I'm interested as to why RIRs dont set the minimum PI allocatable
>> to /24 in order to fit with the current trend.
> In the 2002-3 micro-assignment policy, the RIR's assign a minimum  
> of a /22.

The RIRs all have different policies, and anybody interested in  
finding out the rules for any individual RIR are best advised to  
consult the policy documents published by the RIR in question  
directly. The original question in this thread (that of reachability  
of addresses covered by long-prefix announcements) is profoundly on- 
topic here, however, and explicitly disclaimed by all the RIRs last  
time I checked.

For the ARIN region, the Number Resource Policy Manual currently  
published at <> mentions the following minima:

>>> Single Connection
>>> The minimum block of IP address space assigned by ARIN to end- 
>>> users is a /20. [...]
>>> Multihomed Connection
>>> For end-users who demonstrate an intent to announce the requested  
>>> space in a multihomed fashion, the minimum block of IP address  
>>> space assigned is a /22. [...]
>>> 4.4 Micro-allocation
>>> ARIN will make micro-allocations to critical infrastructure  
>>> providers of the Internet, including public exchange points, core  
>>> DNS service providers (e.g. ICANN-sanctioned root, gTLD and ccTLD  
>>> operators) as well as the RIRs and IANA. These allocations will  
>>> be no longer than a /24 using IPv4 or a /48 using IPv6. [...]

> As far as I know, all of the PI /24's are thus "legacy" in nature.

As the above snippet from the policy manual suggests (and as my  
experience confirms) there are recent assignments made to end users  
by ARIN under the micro-allocation policy which were made with the  
expectation that individual /24s would be advertised globally.  
Clearly these are not the most usual case, as the description of  
those who qualify for such assignments above indicates, but it would  
be a mistake to assume that *all* /24 assignments are legacy.

> From my experience, /24's and longer assigned by RIRs likely to be  
> routed, as well as ones from the old class C space, and people have  
> mostly had problems with /24 PA space in the old Class A and B space.

I'm not aware of widespread filtering of /24s based on assignment  
boundaries in recent years. Can anybody confirm whether this is still  
a real problem?

The real problem today, I thought, was that of allocations or  
assignments being made from fresh /8s that still feature in peoples'  
bogon filters.


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