MAN page from PLD aggregate-1.6-1.athlon.rpm

AGGREGATE

Section: User Commands (1)
Updated: 2001 November 2
Index

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, andperforms two optimisations to attempt to reduce the length ofthe prefix list.

The first optimisation is to remove any supplied prefixes whichare superfluous because they are already included in anothersupplied prefix. For example, 203.97.2.0/24 would be removedif 203.97.0.0/17 was also supplied.

The second optimisation identifies adjacent prefixes that canbe 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 singleprefix 203.97.2.0/23.

OPTIONS

-m max-length: Sets the maximum prefix length for entries read from stdinmax_lengthbits. The default is 32. Prefixes with longer lengths will bediscarded prior to processing.
-o max-opt-length: Sets the maximum prefix length for optimisation tomax-opt-lengthbits. The default is 32. Prefixes with longer lengths will notbe subject to optimisation.
-p default-length: Sets the default prefix length. There is no default; withoutthis option a prefix without a mask length is treated as invalid.Use-p 32 -m 32 -o 32to aggregate a list of host routes specified as bare addresses,for example.
-q: Sets quiet mode -- instructsaggregatenever to generate warning messages or other output on stderr.
-t: Silently truncate prefixes that seem to have an inconsistentprefix: e.g. an input prefix 203.97.2.226/24 would be truncatedto 203.97.2.0/24. Without this option an input prefix203.97.2.226/24 would not be accepted, and a warning aboutthe inconsistent mask would be generated.
-v: Sets verbose mode. This changes the output format to displaythe source line number that the prefix was obtained from,together with a preceding "-" to indicate a route that can besuppressed, or a "+" to indicate a shorter-prefix aggregatethat was added byaggregateas an adjacency optimisation. Note that verbose output continueseven if -q is selected.

DIAGNOSTICS

Aggregateexits 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 byaggregate(output shown using the-vflag):

  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 underthe single prefix 193.58.204.0/21, and 194.126.134.0/23 wassuppressed because it was included in 194.126.132.0/22. The numberin square brackets at the beginning of each line indicates theoriginal line number, or zero for new prefixes that wereintroduced byaggregate.

The output without the-vflag 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

HISTORY

Aggregatewas written by Joe Abley <jableyAATTmfnx.net>, and has been reasonablywell tested. It is suitable for reducing customer prefix filters forproduction use without extensive hand-proving of results.

Autoconf bits were donated by Michael Shields <michael.shieldsAATTmfn.com>.The-toption was suggested by Robin Johnson <robbat2AATTfermi.orbis-terrarum.net>,and the treatment of leading zeros on octet parsing was changed followingcomments from Arnold Nipper <arnoldAATTnipper.de>.

An early version ofaggregatewould attempt to combine adjacent prefixes regardless of whetherthe first prefix lay on an appropriate bit boundary or not (pointed outwith great restraint by Robert Noland <rnolandAATT2hip.net>).

BUGS

Common unix parsing of IPv4 addresses understands the representationof individual octets in octal or hexadecimal, following a "0" or"0x" prefix, respectively. That convention has been deliberatelydisabled here, since resources such as the IRR do not follow theconvention, and confusion can result.

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

This document was created byman2html,using the manual pages.