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Man Pages


Manual Reference Pages  -  ACLGEN (1)

NAME

aclgen - create optimized access lists

CONTENTS

Synopsis
Description
Options
Examples
Bugs
Author

SYNOPSIS

aclgen [-h] [-p] [-i] [-m permit,deny ] [-f format-string ] [-t trace-flags ] [ input_file ]

DESCRIPTION

aclgen builds optimized IP access lists. It is primarily intended for use in large scripts that generate access lists, network lists, or series of static routes from various input sources, e.g. RIPE database route or inetnum objects.

aclgen reads a series of IP address specifications, then computes the most compact classless notation of listed address ranges. The input address expressions may be inclusive or exclusive. Meanwhile the program reads the input it builds internally a binary tree representing the whole address space. After reading the input data, aclgen makes several optimizations on the tree on order to generate the smallest possible graph corresponding to the input address expresions.

Each input line may contain one address expression or a comment. The program accepts wide variety of input formats.
address/prefix
  address is the usual dotted decimal representation, prefix is the number of significant bits between 0 and 32.
address mask
  Similar to the above form but the signifcant bits are represented by the dotted decimal mask . Contiguous netmasks only are allowed. However no matter if zero and one bits are left or right. So 255.255.192.0 is equal to 0.0.63.255. No difference between "mask" and "wildcard" specification. So there is a minor ambiguity with mask 0.0.0.0 (say 255.255.255.255). In that case the program assumes 32 significant bits, if the address is not 0.0.0.0, and thinks 0.0.0.0/0 otherwise. (That means, that the address expression 0.0.0.0/32 has no eqivalent ‘ address mask ’ form. However this is probably not a serious restriction.)

address-address
  Inclusive range of addresses. The dash may be surrounded by any number of spaces and/or tabulators.
address
  The old classful address. However if the address does’n meet his "natural" netmask, i.e. "host part" is not zero, the program treats the input expression as host address ( address /32).
Address specifications may be preceded by a modifier. Modifiers may be positive or negative. The default modifier is positive. The acceptable input modifiers are

       positive   negative
       -------------------
       +          -
       permit     deny
       yes        no

Modifiers are case insensitive, the default is positive.

The input address list is preceded by an implicit
deny 0.0.0.0/32
expression. In other words the generated filter list will discard the unspecified part of the address space unless you override it with an explicit
permit 0.0.0.0/32
line in the input file. This behaviour is not affected by the -i option. (See below.)

Empty lines, leading/trailing spaces and any characters from ‘#’ to the end of line are ignored as well as unparseable lines.

If the input line begins with ‘*’ aclgen prints the currents state of the binary tree of the address space. This is for debugging purposes only.

The input is read from infile or from the standard input if no input file specified. ‘-’ means stdin too.

OPTIONS

-h Print version and usage then exit.
-s Silent mode. Warnings are supressed.
-i Invert modifiers of all input lines. It does’n affect the implicit ‘deny 0.0.0.0/0’ statement. (See above.)
-p Force "positive" output. If -p is specified, the output contains no ‘deny’ specifications. Useful when generating routing tables or network lists.
-d level
  Switch on diagnostics. ‘level’ is the sum of one or more trace flags:
    1  show input parsing
    2  print raw tree
    4  print optimized tree
   16  debug optimization step 1
   32  debug optimization step 2
   64  debug optimization step 3
  128  debug optimization step 4

-f format-string
  Format-string is a printf(3) like format specification of output lines. The recognized conversion specifications are:

%a  address (dotted decimal)
%k  mask (dotted decimal)
%w  wildcard bits (dotted decimal, binary complement of %k)
%p  prefix
%m  modifier (permit/deny by default)
%%  the ‘%’ itself

The default format string is "%m %a %w". If you specify a format string without %m, the program automatically turns on the -p option.

-m permit-string,deny-string
  Change the modifiers. The default modifiers are ’ permit ’ for addresses to accept and ’ deny ’ for addresses to reject.

EXAMPLES

The examples below follow the syntax of Cisco IOS configuration commands.

Basic functionality

  % aclgen -f "access-list 83 %m %a %w" << END
  > 192.168.10.0-192.168.15.0    # range of 6 C classes
  > 192.168.16.0/23              # classless
  > 192.168.18.0                 # classful
  > 192.168.19.0                 # classful
  > 192.168.32.0 255.255.224.0   # masked
  > 192.168.32.5                 # host
  > 192.168.80.7                 # host
  > END
  access-list 83 deny   192.168.8.0 0.0.1.255
  access-list 83 permit 192.168.8.0 0.0.7.255
  access-list 83 permit 192.168.16.0 0.0.3.255
  access-list 83 permit 192.168.32.0 0.0.31.255
  access-list 83 permit 192.168.80.7 0.0.0.0
  access-list 83 deny   0.0.0.0 255.255.255.255
  %

The same list but inverted

  % aclgen -f "access-list 83 %m %a %w" -m "deny  ,permit" << END
  > 192.168.10.0-192.168.15.0    # range of 6 C classes
  > 192.168.16.0/23              # classless
  > 192.168.18.0                 # classful
  > 192.168.19.0                 # classful
  > 192.168.32.0 255.255.224.0   # masked
  > 192.168.32.5                 # host
  > 192.168.80.7                 # host
  > END
  access-list 83 permit 192.168.8.0 0.0.1.255
  access-list 83 deny   192.168.8.0 0.0.7.255
  access-list 83 deny   192.168.16.0 0.0.3.255
  access-list 83 deny   192.168.32.0 0.0.31.255
  access-list 83 deny   192.168.80.7 0.0.0.0
  access-list 83 permit 0.0.0.0 255.255.255.255
  %

Classless BGP announcements

  % aclgen -p -f "network %a %k" <<END
  > 192.168.10.0-192.168.15.0    # range of 6 C classes
  > 192.168.16.0/23              # classless
  > 192.168.18.0                 # classful
  > 192.168.19.0                 # classful
  > 192.168.32.0 255.255.224.0   # masked
  > 192.168.32.5                 # host
  > 192.168.80.7                 # host
  END
  network 192.168.10.0 255.255.254.0
  network 192.168.12.0 255.255.252.0
  network 192.168.16.0 255.255.252.0
  network 192.168.32.0 255.255.224.0
  network 192.168.80.7 255.255.255.255
  %

Static routes

  % aclgen -p -f "ip route %a %k 10.0.3.2" <<END
  > 192.168.10.0-192.168.15.0    # range of 6 C classes
  > no 192.168.13.128/26         # hole in the block above
  > 192.168.16.0/23              # classless
  > 192.168.18.0                 # classful
  > 192.168.19.0                 # classful
  > 192.168.32.0 255.255.224.0   # masked
  > END
  ip route 192.168.10.0 255.255.254.0 10.0.3.2
  ip route 192.168.12.0 255.255.255.0 10.0.3.2
  ip route 192.168.13.0 255.255.255.128 10.0.3.2
  ip route 192.168.13.192 255.255.255.192 10.0.3.2
  ip route 192.168.14.0 255.255.254.0 10.0.3.2
  ip route 192.168.16.0 255.255.252.0 10.0.3.2
  ip route 192.168.32.0 255.255.224.0 10.0.3.2
  %

BUGS

This manpage is written in "Hunglish". ;-)

AUTHOR

Written by Gabor Kiss <kissg@sztaki.hu>

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--> ACLGEN (1) June 21, 1997

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