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AGGREGATE(1)		    General Commands Manual		  AGGREGATE(1)

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

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

DESCRIPTION
       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, 203.97.2.0/24 would	be removed if 203.97.0.0/17  was  also
       supplied.

       The  second  optimisation identifies adjacent prefixes that can be com-
       bined under a single, shorter-length prefix. For	example, 203.97.2.0/24
       and 203.97.3.0/24 can be	combined into the single prefix	203.97.2.0/23.

OPTIONS
       -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 203.97.2.226/24 would be  truncated
	      to   203.97.2.0/24.   Without   this   option  an	 input	prefix
	      203.97.2.226/24 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.
DIAGNOSTICS
       Aggregate exits 0 on success, and >0 if an error	occurs.

EXAMPLES
       The following list of prefixes:

	 193.58.204.0/22
	 193.58.208.0/22
	 193.193.160.0/22
	 193.193.168.0/22
	 193.243.164.0/22
	 194.126.128.0/22
	 194.126.132.0/22
	 194.126.134.0/23
	 194.151.128.0/19
	 195.42.240.0/21
	 195.240.0.0/16
	 195.241.0.0/16

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

	 aggregate: maximum prefix length permitted will be 24
	 [    0] + 193.58.204.0/21
	 [    1] - 193.58.204.0/22
	 [    2] - 193.58.208.0/22
	 [    3]   193.193.160.0/22
	 [    4]   193.193.168.0/22
	 [    5]   193.243.164.0/22
	 [    0] + 194.126.128.0/21
	 [    6] - 194.126.128.0/22
	 [    7] - 194.126.132.0/22
	 [    8] - 194.126.134.0/23
	 [    9]   194.151.128.0/19
	 [   10]   195.42.240.0/21
	 [    0] + 195.240.0.0/15
	 [   11] - 195.240.0.0/16
	 [   12] - 195.241.0.0/16

       Note that 193.58.204.0/22 and 193.58.208.0/22 were combined  under  the
       single  prefix 193.58.204.0/21, and 194.126.134.0/23 was	suppressed be-
       cause it	was included in	194.126.132.0/22. 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:

	 193.58.204.0/21
	 193.193.160.0/22
	 193.193.168.0/22
	 193.243.164.0/22
	 194.126.128.0/21
	 194.151.128.0/19
	 195.42.240.0/21
	 195.240.0.0/15

SEE ALSO
       aggregate-ios(1)

HISTORY
       Aggregate was written by	Joe Abley <jabley@mfnx.net>, 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
       <michael.shields@mfn.com>.  The -t option was suggested by Robin	 John-
       son  <robbat2@fermi.orbis-terrarum.net>,	 and  the treatment of leading
       zeros on	octet parsing was changed following comments from Arnold  Nip-
       per <arnold@nipper.de>.

       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
       <rnoland@2hip.net>).

BUGS
       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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