aggregate

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
       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
       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 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
       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
       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
       reasonably well tested. It is suitable for reducing customer prefix
       filters 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 <robbat2@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)