aggregate6 - a fast versatile prefix list compressor

Julien Goodwin nanog at
Fri Dec 1 10:09:38 CST 2017

On 01/12/17 07:27, Job Snijders wrote:
> Someone suggested I should clarify what 'aggregate6' actually does :-)
> aggregate6 takes a list of IPv4 and/or IPv6 prefixes in conventional
> format, and performs two optimisations to attempt to reduce the length
> of the prefix list.
> The first optimisation is to remove any supplied prefixes which are
> superfluous because they are already included in another supplied
> prefix. For example, 2001:67c:208c:10::/64 would be removed if
> 2001:67c:208c::/48 was also supplied.
> The second optimisation identifies adjacent prefixes that can be
> combined under a single, shorter-length prefix. For example,
> 2001:67c:208c::/48 and 2001:67c:208d::/48 can be combined into the
> single prefix 2001:67c:208c::/47. As an IPv4 exampl: and
> can be joined into

Will it catch cases like: ->

> The above two optimalisations are useful in context of firewall rule
> generation or generation of BGP prefix-list filters.

Or being a nice citizen and rationalising your announcements.

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