Approach to allocating netblocks

Chris Grundemann cgrundemann at
Wed Jan 14 16:50:21 UTC 2009

On Wed, Jan 14, 2009 at 09:05, Frank Bulk <frnkblk at> wrote:
> For the first time we have our own ARIN-assigned netblocks that we can now
> split out and divide to our customers.
> What's the best approach to handing out /30's, /29's, etc. that is efficient
> as possible but allows for customers to expand their allocation to a
> neighboring block?

We pay much more attn to efficient utilization and advertisement
aggregation than to ensuring that customers have contiguous blocks.

For example, we internally assign a /24 to a given PE router and then
assign from it straight through; 0/30, 4/30, 8/29, etc. as customers
get turned up or request more space.  Then when it's used up, we add
another...  Although it is neat and tidy to have contiguous blocks
everywhere, the cost to benefit doesn't seem to be there so we focus
on aggregation at transition points such as edge to backbone, backbone
to peers, etc.


> I was thinking of having one /24 for each block size, and then do the divide
> and conquer approach by allocating the first /30, for example, as 0 and 128,
> then next two at 64 and 192, etc.  Once there's only one /30 free between
> each allocation, I would start using another /24.  Of course, that would
> mean 50% (or less) utilization.
> Ideas?
> Frank

Chris Grundemann

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