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 superfluous because they are already included in another supplied  pre-
       fix. 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 combined 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 invalid.   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 aggre-
              gate 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
       because it was included in 194.126.132.0/22. The number in square brackets at the beginning of each line indicates the original  line  num-
       ber, 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 reasonably 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  Johnson  <rob-
       bat2@fermi.orbis-terrarum.net>,  and  the  treatment  of  leading  zeros on octet parsing was changed following comments from Arnold Nipper
       <arnold@nipper.de>.

       An early version of aggregate would attempt to combine adjacent prefixes 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"
       prefix, respectively. That convention has been deliberately disabled here, since resources such as the IRR do not  follow  the  convention,
       and confusion 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)