Smallest netblock that providers will accept?

Anton Kapela tkapela at
Tue Aug 19 00:26:21 CDT 2008

On Mon, Aug 18, 2008 at 10:05 PM, Kevin Blackham <blackham at> wrote:
> Your assumption is generally true with most any provider. They may
> even accept something smaller, but it won't make it very far if less
> than /24. It's also a good idea to announce a covering prefix in case
> some peer network filters on IRR minimums.

The part that Kevin spares you from reading is the "please don't"
part. If your goal is to provide HA or DR-like aspects to some
$single_application end-site and all you can justify is a one-time
allocation of a /24, consider other options. There are already enough
/24's in the DFZ both from end-site multihomers and wreckless
deaggregation (and those who refuse to build a backbone and/or insist
that POP-level convergence towards their network is everyone elses
problem, not theirs).

Instead of going down this road, I would suggest that you:

-call up cisco and purchase a GSS (global dns lb with application
availability probes, etc)


-attach your site to a pair of willing upstreams who already have a
larger prefix aggregate set aside (say a /18 or something) for
end-site multihoming, in which it is expected that the prefix will be
originated from disparate AS's (neither of which is the actual


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