Single organizations with multi-homed, discrete networks

Richard Jimmerson richardj at
Wed May 9 08:17:16 EDT 2001

During the open microphone session at the ARIN public policy
meeting last month the issue of single organizations with 
multi-homed, discrete networks was raised.

When these organizations receive an allocation from ARIN, they 
split it up and assign a minimum of a /20 to each multi-homed, 
discrete network.  There is a concern that a longer prefix 
would be filtered.  Although this satisfies their concerns about 
filtering, it often conflicts with ARIN's policy for requesting 
additional IP address space.  ARIN's policy states an organization 
must demonstrate 80% of their previous allocation is efficiently 
utilized before their request for additional IP address space will 
be reviewed.  

Apply the following scenario:  An ISP receives a /18 from ARIN and 
splits it up into four /20s -- one for each of their multi-homed, 
discrete networks.  After some time, one of those networks may 
have utilized 75% of its /20, but the others may be growing at a 
slower rate and only be at 25% each.  The network that is at 75% 
would soon need additional IP address space, but the overall 
utilization of the /18 obtained from ARIN would only be at 37.5%.  
This would prevent that organization from meeting the criteria 
for obtaining additional IP address space from ARIN.

Knowing this to be the case, the ISP may elect to justify a 
separate maintainer account with ARIN for that single multi-
homed, discrete network.  This eliminates any consideration 
of the growth rate of the other networks when applying for 
additional IP address space.  If an ISP was to do this for 
other networks they would soon have many maintainer accounts 
open with ARIN.

Should ARIN make a change to its policy that takes this issue 
into consideration and prevents organizations from having to 
open multiple maintainer accounts to meet the IP addressing 
needs of their multi-homed, discrete networks?

This question is posed as a continuation of the discussion 
that took place at the recent public policy meeting.  Your 
feedback is requested.

Richard Jimmerson
Director of Operations
American Registry for Internet Numbers (ARIN)

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