CIDR Aggregation Tool

Avi Freedman freedman at
Mon Nov 27 16:44:12 UTC 1995

> Perhaps this is just a small error that has to be accepted in your
> measurements, but we are dual homed and require both the aggregate and 
> the specific.
> > 2) When an AS advertises both an aggregate and a specific, the specific 
> >    is 'dropped' by the aggregator. If the input is:
> >    {,}, the output will be:
> >    {} ( will be dropped).

The was a random example.  I hope that's not you :)

There are no "value" judgements made by the tool - it's just suggesting
aggregates.  And if we see an aggregate and a specific, both set to 
the same next-hop, it's quite likely that it's the same AS announcing 
both routes, and that they (your transit provider(s)) could do the 
aggregation themselves - but the tool *is* deficient in that right now 
it doesn't consider AS-paths.

As an example, picking an IP for (

Our route table has:
*>        <--- agis
*>        <--- mci
*>        <--- agis
*>        <--- agis

So if 198.111.252/23 is suggested as an aggregate for the
(AGIS) target, that's because it looks like AGIS could in fact announce instead of 198.111.252/0 and


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