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AGGREGATE(1)		    General Commands Manual		  AGGREGATE(1)

       aggregate  -  optimise a	list of	route prefixes to help make nice short

       aggregate [-m max-length] [-o max-opt-length] [-p default-length]  [-q]
       [-t] [-v]

       Takes  a	list of	prefixes in conventional format	on stdin, 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 su-
       perfluous because they are already included in another supplied prefix.
       For example, would	be removed if  was  also

       The  second  optimisation identifies adjacent prefixes that can be com-
       bined under a single, shorter-length prefix. For	example,
       and can be	combined into the single prefix

       -m max-length
	      Sets  the	 maximum  prefix  length  for  entries read from stdin
	      max_length bits. The default is 32. Prefixes with	longer lengths
	      will be discarded	prior to processing.

       -o max-opt-length
	      Sets  the	 maximum  prefix  length  for optimisation to max-opt-
	      length bits. The default is 32.  Prefixes	 with  longer  lengths
	      will not be subject to optimisation.

       -p default-length
	      Sets  the	 default  prefix  length. There	is no default; without
	      this option a prefix without a mask length  is  treated  as  in-
	      valid.  Use -p 32	-m 32 -o 32 to aggregate a list	of host	routes
	      specified	as bare	addresses, for example.

       -q     Sets quiet mode -- instructs aggregate never to generate warning
	      messages or other	output on stderr.

       -t     Silently	truncate  prefixes  that  seem to have an inconsistent
	      prefix: e.g. an input prefix would be  truncated
	      to   Without   this   option  an	 input	prefix would not	be accepted, and a warning  about  the
	      inconsistent mask	would be generated.

       -v     Sets verbose mode. This changes the output format	to display the
	      source line number that the prefix was obtained  from,  together
	      with a preceding "-" to indicate a route that can	be suppressed,
	      or a "+" to indicate a shorter-prefix aggregate that  was	 added
	      by  aggregate  as	 an  adjacency optimisation. Note that verbose
	      output continues even if -q is selected.
       Aggregate exits 0 on success, and >0 if an error	occurs.

       The following list of prefixes:

       is optimised as followed	by aggregate (output shown using the -v	flag):

	 aggregate: maximum prefix length permitted will be 24
	 [    0] +
	 [    1] -
	 [    2] -
	 [    3]
	 [    4]
	 [    5]
	 [    0] +
	 [    6] -
	 [    7] -
	 [    8] -
	 [    9]
	 [   10]
	 [    0] +
	 [   11] -
	 [   12] -

       Note that and were combined  under  the
       single  prefix, and was	suppressed be-
       cause it	was included in The number in	square	brack-
       ets  at	the beginning of each line indicates the original line number,
       or zero for new prefixes	that were introduced by	aggregate.

       The output without the -v flag is as follows:


       Aggregate was written by	Joe Abley <>, and has been rea-
       sonably	well  tested. It is suitable for reducing customer prefix fil-
       ters for	production use without extensive hand-proving of results.

       Autoconf	    bits     were     donated	  by	  Michael      Shields
       <>.   The	-t option was suggested	by Robin John-
       son <>, and the	treatment  of  leading
       zeros  on octet parsing was changed following comments from Arnold Nip-
       per <>.

       An early	version	of aggregate would attempt to  combine	adjacent  pre-
       fixes  regardless of whether the	first prefix lay on an appropriate bit
       boundary	or not (pointed	out with  great	 restraint  by	Robert	Noland

       Common unix parsing of IPv4 addresses understands the representation of
       individual octets in octal or hexadecimal, following a "0" or "0x" pre-
       fix, respectively. That convention has been deliberately	disabled here,
       since resources such as the IRR do not follow the convention, and  con-
       fusion can result.

       For  extremely  sensitive  applications,	judicious use of the -v	option
       together	with a pencil and paper	is probably advisable.

Joe Abley			2001 November 2			  AGGREGATE(1)


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